My son's forts

My son LOVES LOVES LOVES to build caves or forts. The only problem is they are very big and very extensive. And usually require every available blanket, pillow, spare box, whatever. And of course he doesn't just sit in them and enjoy himself. He goes in and out and in and out to where I am constantly fixing them. But.....I realized this could be a good incentive for him to finish those chores. So our new rule is if chores are done in the time limit then he can build a cave/fort for that day. Maybe it will work.