I did a redo of the 45 lb. pork butt cook to see if I could get a 21.6 lb bag of Kingsford to go longer than about 12 hours.
This time I used 2 gallons of hot water in the pan instead of cool water. It was also a calm, warm night, never went below 63 degree. Someone at Weber told me they got 14 hours by starting with a lot of hot coals, setting the top vent 3/4 open, and closing all the bottom vents for the entire cook.
I used foil to plug the gaps in my out-of-round condition and put a full Weber chimney of hot coals over the remainder of a 21.6 lb. bag of Kingsford. Set the vents as instructed. Meat sat at room temp for 1 hour before going into the cooker. I could not get it over 200*F. So I opened just 1 bottom vent 100% and it ran in the low 200's for a long time, then I ended up with 2 bottom vents open 100% toward the end of the cook.
Once again, it started to poop-out at about 11 hours. The meat was done at 11.5 hours. I shook loose the ashes to reveal maybe a chimney-full of partial briquettes in various stages of burning. So it looks like if you want to go much beyond 11 hours with this much meat, you may have to add more fuel.
I'm thinking about trying the pork butt again, but with lump. I'm also thinking about trying two big briskets and Kingsford. That would only be about 26-28 lbs. of meat, maybe the Kingsford would last longer in that case.