A few weeks ago I posted the question about using a second charcoal basket in my Party instead of adding charcoal to the primary basket when needing long burn times. I also posted a pic of the basket I fabbed up.
Anyway at the comp this past weekend I tried out my idea. I was able to put 11 lbs of RO briquettes in the new basket. I used two Weber cubes to light one corner at 9:30 PM. By 10:45 the temp was dialed in at 250. This was with a full water pan and filling it during the entire cook. At 9:30 AM I filled the OEM basket with five pounds of RO briqs and lit a corner with a cube. Right after I wrapped the ribs at 10 AM (big meats already wrapped) I swapped out the baskets. The second basket was about 25% lit. The temps never skipped a beat and there was no dirty smoke. This was so much easier than trying to add charcoal to an expended basket. It allowed me to dump the contents of the ash pan when swapping the baskets which I think was beneficial since the ash was always deep after a long burn.
Bottom line is, I got 11 hours 15 min on the first basket and at least 4 hours on the second. So about 15 hours on 16 lbs of briqs with a 2-3 minute swap out time.