i've only tried them a couple of times and at most ive only beeen able to loot 1.5 loot piles before enemy mobs loot all the others and start attacking. As for leaving i think you just have to run out of bounds on the map.

that being said im not sure if theyre even worth it, esp once youre able to take down enemy lords yourself

You don't have to run out of bounds; you can just Tab-Retreat so long as you're still alive an no enemies are nearby.

Also, as far as I've tried, they're absolutely not worth the time.

They were amazing when I was defeated and released without money nor anything, escencialy I became a looter and selling what 3 equipment before they start mobbing could get was what helped me to rise back

don't let any other looters escape, you get what they looted when you win the scene. check size of loot before you enter to see if its worth it, i don't bother with small.