Im not sure if this is intended or a bug but when clearing out bandits if you kill the leader and leave some bandits alive .The fort will eventually become repopulated with bandits gets a new leader with a bounty on his head. If your careful it means there should be a never ending supply of bandit bounty jobs. Unless of course you hate clearing out forts in witch case dont bother.

Every dungeon will repopulate in 10-30 days IIRC. So yes, it's a never ending supply