Pallas- they will continue to put in effort if it looks like they have a chance to win. Seble explained it during beta that if a SIM doesn't think they have a chance to win they will move on to another player. So it might be a good strategy to drive a SIM out right away so they don't continue to battle.
He never did explain how much of their budget they use or how they would use it or if they can run out of money. Nothing like that.