My thoughts are a mod where you game go retro under a list of it own.
Math. Total score = years/4 for every 1/4 year not passed 1d12 (12 dice) sales (-number=0)
when run out they give like 1d"score/4 round down" sales until 15 years passed = 0.
Marking in creation if it shall be made Retro later.

Make it retro shall cost to keep up like 500-1000 for every sale.
This Make your products more realistic, vanilla its fells a little off, that you can't have 2 game on market at the same time, retro make it more stabil. (You can pull it of market before)

A thing can be when you pass 2000 all mastered (38 and +) games can be made retro again (Can stack games in to a pack if some are lower), so you can remake them but this will cost you some time and money. the stacking just add up time its out on sales, so if 12 game stack it means 12 sale before count, and instead it is 1/4 years-years pass of main game, but then they are removed from make retro list and die off after that. (make retro once more all so remove it from marketing).

Take it if you like.