Oh and i made a cover for the i take vent so i could open or close it.
From what I could tell it maintained 250 no problem at all for about 5 hours on the first load of charcoal. I didnt touch it except when I added more charcoal about 5 hours and 15 minutes into it. I added probably about 5 lbs total while cooking.
It was for about 14 hours but the second time I added charcoal the temp had dropped to about 200 before I got more charcoal in it. The IT was only about 185 when I pulled it though.