I think that haunt length is based largely on the (misguided) notion that it's a haunts duty to get people to pee their pants. Some shorter haunts due it by trying to scare people so much they have to pee. Some other haunts use the strategy of keeping people in the haunt so long, they just can't hold it anymore. Some do both. My only explaination is that one of the secrets of the inner circles of one of the haunt organizations is that they own a lot of stock in mops and/or cleaning products and are attempting to create demand for those products.