I failed on fire duty last night. Only slept for 3.5 hours and woke up to no coals. I have no idea why the fires aren't burning longer. I'm setting the damper half open to slow the burn.

Half open would have me without coals as well. But since your wood isn't real dry, any more closed and it probably would go out. Are the pieces of a size you can get a lot in without a lot of air space?