With rimmsqol, which is literally the best mod ever made, I set the maturation times to custom values. I use 40x smart aging for humanlikes so the value may not be universal but I set most of them to between 30 and 48 days depending on other features of the creature like breeding times, market value, and if they give animal product besides meat and leather. The biggest ones like brachiosaurus for example to between 48 and 56. My logic was the thrumbo is suppose to by rimworld lore be a ancient long lived creature and has a massive maturation time time of a whole year. But you have to remember, thrumbo fur is a dang near perfect leather and they give thrumbo horns which are both great melee weapons as well as a good to sell for a decent amount of silver. Add on the thrumbos battle capabilities with everything else and the maturation time added onto the 20 day gestation period isn't too bad in players eyes, a thrumbo farm if you got the trees or hay for it can be VERY useful. Something you can see with genetics expanded with how they lean on the differences and variations of their own thrumbo hybrids variants even if sarg has always had a bit of a issue making decent breeding and maturing times for their modded creatures.

As for the dinosaurs, sure they can be good in a fight and a bit tanky but in theory a thrumbo or two should still be able to take one in a fight even if they get injured a bit. Thrumbos are deadly after all. You can change a few other values to show this alongside the lower maturation time. Lowering sauropod attack damage a little but keep their tanky bulk. Sauropods didn't exactly attack others except in self defense after all and even then they were large and slow in a lot of cases so attack speed would logically be lower too. But their size would still give them a decent attack damage, but not too large. To off set the maturation times plus breeding times even more as well as balance their meat and leather output you can lean into how rimworld balances keeping pet thrumbos. Simply put, the bigger the creature the more it eats. In the case of a brachiosaurus it should not only eat a fair bit more then a thrumbo but have a larger stomache with slightly faster food loss to simulate such a large animals metabolism at work to keep it's massive body alive. This means to keep a farm of such a massive creature you would need A LOT of food making the meat income just slightly more then your feeding them. That makes them a inefficient source of food and leather but still a possibility to farm if you do it right and want a lot of dino leather for whatever reason.

Lower the effectiveness of the leather due to the bulk player gets would also balance the leather income. Basically use simple math logic: The leather came from such a big creature that when you only use a small fragment of the leather you get to make clothes out of you get significantly less effective protection compared to the creatue it came from due to a lower density and surface volume. Basically, the thing that made the creature so protected with such skin is it's size and how much skin covered the whole thing. Even if you cut a part their was still a lot of creature to injure to kill it. In the case of a humanlike wearing the skin they have less size and the leather would be far less effective with less coverage. This means that the leather should likely be good at blunt and possibly decent at insulation due to it's thickness but other forms of damage like sharp it can't really protect against well since carnivore teeth could still cut through it when it was alive. This means even if a player got a lot of leather from a creature muffalo's and other creatures that give leather or wool good at insulation are still better and more efficient sources and while the leather was good a blunt there are slightly better leather for protection out there.

Farm animals like pigs, chickens, cows, or even some wild animals are still better for meat production due to being more efficient to farm but giving players the option even if it's inefficient to farm sauropods would fit the balance of the game. Thrumbos are inefficient due to how much they eat but you get a decent battle animal, good leather, a decent amount of meat, and a horn with a few uses. Sauropods should in comparison give players a large and tanky animal with lower damage output then a thrumbo due to only having their size to their advantage in battle( no horn, claws, or sharp teeth ), a large amount of less effective leather but still good for making a large amount of clothes, and a lot of meat that's offset a bit by how much you had to feed them to get a fully grown creature over time.

I have no clue but im going off the logic rimworld vanilla uses to balance some of it's animals. Don't know if it'll work here but figured I would list all of my thoughts on it regardless so enjoy this wall of text lol

I would say whatever the maturation/gestation times are for the thrumbo, use those same times for any super-gigantic dinos, even if they are much larger than the thrumbo. Reasonably realistic and reasonably balanced for game play. If a blue whale gan gestate a baby whale that is bigger than an elephant calf faster than an elephant can gestate a smaller baby elephant calf, then a sauropod can make a baby that is bigger than a thrumbo calf in the same time as a thrumbo takes. Same for maturation. Just needs to take a "long" time, but not so long that there is no point in trying to breed them in a 3 year game. That part is the gameplay consideration/ balance.

A decent idea but a few issues, for one thing egg layers will be a issues if that was solution used in a blanket fashion and since most of the creatures in the mod are egg layers.. yeah. What I mean is if all big creatures have a 20 day gestation time then things will get messy, specifically for animals that are suppose to give unfertilized eggs as a feature. Don't have to look far for what I mean since all but two of the animals in dinosauria had 30 day gestation times. Even the compy which gave unfertilized eggs. That was one unfertilized egg ever 30 days which was just bad balance for multiple reasons.

My counter argument is use incubation times instead. Gestation times for egg layers should logically be less then their incubation times in most cases. Just look at some vanilla birds to see what I mean. A ostrich for example has a incubation time of around 7 days but lays eggs in less time then that. So for example super big creatures you balance in similar ways to my previous comment but also for creatures that have alternate uses or features like wool you could possible go over the thrumbo gestation time a bit. Humans in the game actually have a gestation time themselves in vanilla rimworld, a little known fact there. Before 1.3 it was 45 days but post 1.3 it's 30.

To put this into a example lets say a brachiosaurus, one of the largest animals in the mod, had a gestation/egg laying period of around 9 but a incubation time of around 19. Let's also say it's maturation time is 48 days. This puts it's total breeding time at 24 days as a whole. 6 less then a human but also 4 more then a thrumbo. It's maturation time is also 12 days less then a thrumbo since it takes a whole ingame year for a thrumbo to grow up if I remember right. The reasoning being a thrumbo has a life expectancy of over 200, a brachiosaurus will have less then that so matures faster then the thrumbo. A brachiosaurus is a peaceful herbivore even if their poor parenting leaves a lot to be desired and was big enough to not get attacked often or at all in most cases. This means it's attack power is purely it's bulk and size so defensively it's good but offensively it's decent but not as good as a thrumbo. It's too dumb from what most scientists claim to be a pack animal so it's only use will be it's meat and leather or it's eggs wince fertilized eggs can still be eaten. With a 48 day maturation time but a breeding time fitting it's features and certain aspects of the species due to the amount of meat and limited uses will put it in a "farm animal" classification and while annoying to breed or feed would give a massive mount of meat and leather.

The reasoning is simple. Thrumbos are animals and by lore "one of the oldest creatures in the universe" which means in the rimworld backstory the things can live very long lives. We see this with it's massive life expectancy. They breed slowly but since 1.3 still viable to breed if you have the food for upkeep. Logically most mods should use the thumbo, one of the flagship animals for the game, to balance their animals around. No animal should take longer then a thrumbo to breed unless it's a egg layer, and which point it's incubation time should never be more then 15 days and it's egg laying never more the 10 days since humans are one of the longest gestation times in the game. No creature should take longer to mature then a thrumbo. No egg laying animal should actually go over the 20 day breeding time without a good reason, specifically if there is no other way to balance them or their capabilities. For a brachiosaurus that reason is it's leather and meat amount and lower maturation time. If the leather is nerfed then a lower breeding time should also be used. Realism is awesome and personally I would perfer it but we have to remember this is rimworld and balance is needed to keep the feel of the game to am extent. The developers of mods need to find a middle ground between realism, balance, and keeping gameplay interesting.

Which is where my brachiosarus example comes in. It's a massive animal, the main focus of this discussion. Doing it like I stated would give players a chance to breed and use them as utility animals in some form while keeping them invested and interested. Humans as a whole have short attention spans if things take too long since they'll lose interest, the massive breeding times pre-1.3 was one of the main complaints until it got it's 1.3 overhaul. The thrumbo took the longest with a whopping 80 days pre-1.3 and still have the longest breeding time besdies possible a egg layer or two. So logically no animal should take as long for the same thing. Humans take about 9 months irl to gestate but 30 days ingame. The thrumbo is a long lived creature so biologically it should take longer then a human to gestate. But from a gameplay standpoint humans are more valuable/useful for players colonies for obvious reasons. Not to mention their normal gestation times are only used with pregancy mods that allow them to breed, but as anyone whos used such mods like me can tell you the 30 days works from a balance perspective regardless. Even more so for legacy type playthroughs where you go through the generations of a colony using such mods and faster aging mods like I personally enjoy.

Regardless I think I wrote too much here and now im in the mood to play some rimworld so ill check here again later on. Hopefully I didn't sound too much like a pretentious nerdy rimworld fangirl despite the 3000 hours I have in the game lol