When I play a game, and manage to get the upper hand, I often leave the AI with one or two villager types and enough to build up again. But then the AI seems to stop thinking:
* It farms away forever but does not produce new villagers.
* It send villagers/gatherers etc. to far away places for gold and wood - often repeatably past my watch-towers, which gets them killed.
* If I leave it near an abandoned settlement, it makes no attempt to settle.
Does the AI just give up at some stage?
Sangoma