I've done several 4 butt cooks on my Large. The longest going 22 hours and the shortest about 18 hours. That is until this weekend. Had a picnic at 4pm Saturday. Put 4 butts on the egg at 8pm Friday night figuring I could get them done by 2pm Saturday and then let them rest. They however had other plans. all 4 hit 190 at 6am Saturday morning, a full 10 hours before I needed them. It blew my mind. 28 lbs in 10 hours. And, I didn't push them at all. I started at 250 grid but brought the temp down to 230 grid when I saw how quick they were cooking, and never foiled. Didn't matter. Had my phone on my bed side table all night checking their progress. Every time I peaked at it I just said to myself there is no freaking way. The meat probes have to be off, on bone, in some fat pocket or something. At 6am they were reading 190 and I hit each one with my thermapen just to see. Sure enough they were all done.
Needless to say I kept them warm in a cooler for about 5 hours and then in the oven on 175 warm for the the other 5 till time to eat. They were perfect of course.