You can run your kettle like this: You'll get 13 hours of burn time without need to refuel. Light 12 briquettes and once ashed over put them on top of one end of the unlit ones...it'll contact burn for about 13 hours with an almost full ring. Top vent wide open and bottom varies to control temp.
Note: only a half ring is pictured. That will burn about 6 hours.
Shot at 2012-06-03