I burn some pretty crappy wood. Willow, red cedar, cottonwood, I'm not picky about species. Anything less than 24 hours on a low setting and with a full firebox is abnormal. The cycling and temps sound pretty normal but the rapid wood consumption is not right. How are you deciding that you are out of wood? I get 24 hours from when cat goes active to cat going inactive. Seems to be a pretty dependable way to measure burn time.