I do 18+ pound turkeys all the time and it takes me between 6 and 8 hours. My temps usually run between 250 and 275. As I am writing this I have 2 in the new smoker I got for Christmas from the family. They weigh 18 and 20 pounds, and I'm fighting the cold and wind trying to get them done. Got a wind break up made from insulated duct work and the temps are only running around 235 + - , so its gonna take a bit longer. Sure hope i get them done by 6:00, I think they will as they are at 120 now and its only 2.5 hours into smoke. Hope that helps you out