I can believe that they are cooking for 15 to 18 hours. When I first started cooking I would let a butt or brisket go at 225 on the BGE for 16 hours minimum. I did not foil back then and the stall would last for up to 7 hours aroun 160 it. If they are doing whole shoulder or 20 pound packers with no foiling then I can see going one hour per pound at 225. I don't understand doing this however when you can get the same results in 8 hours with slightly higher temps and foil.
Smoke in the Mountains BBQ Team; offset reverse flow