I don't know about where you live but I go to a local rock / landscape place and get a 50 pound bag of large chunks of coal, just small enough to fit in the door. Get the tent warmed up with wood about an hour before you go to sleep to get some good coals then put about 4 or 5 chunks of coal in there and close the vent to where it gets just enough air to smolder. You might have to stoke it once but it beats 2 or 3 times a night. The bag usually lasts about 2 weeks, seasons for us here, or so.