EbS-P
Minister of Fire
My two cents. Leave a good layer of ash. I find the deeper the coal bed on my last load the longer the burn (with enough room left to get a good load in). Last load I reload hot and get the secondaries going then shut it all the way down. A big split in the bottom back helps. I have a blower I think it might help keep the firebox temps lower to extend the burn time with my setup. I consider overnight enough coals for an easy morning relight. I usually stay up a bit later on cold nights but I’m thinking a middle of the night 2-4am reload with just enough wood to throw it on set it and forget it might be better.