Ran mine fully open on all vents with a full water pan for 11 hours of a 12 hour cook this past weekend. I only choked the bottom vents a couple hours in when I was getting into the 280's. Temp range was typically 240-270. Started with the bottom full of charcoal and wood chunks, and dumped on a full chimney of coals. Let it go for an hour when the smoke got clean before adding meat. Any time the temp would dip, I'd stoke the coals a little and temp would go back up. Did add a fully lit chimney of coals about 8 hours in which spiked the temp to 300, but then added more water and that seemed to bring my temp back down to the 260's after a few minutes.
My cooking conditions are probably a little different than most since I live a mile high. It's also pretty dry in my area of CO, so I like to keep the cook chamber as humid as possible. Conditions were calm during this cook.