In city battles (with me attacking) I don't mind the AI exhausting itself running around. Running around is a serious disadvantage for them, but to balance that they have the serious advantage of being able to fight to the death on the central city square, intead of routing.

Historically speaking, once the city square is surrounded, the enemy should surrender as further resistance is pointless. But instead RTW forces a fight to the death - that benefits the AI as they are usually the ones on the defensive.

In open field battles, I try to avoid the AI exhausting itself, by placing my army as close to the enemy as possible, even if that means giving up a hill position. Once the battle starts, I sometimes allow myself to redeploy my army to the top of the hill, but I've got to run to get there, which means my troops become just as exhausted as the enemy.