I got a 13 hour burn time with my 30 on this recent cold wave. It was 14 degrees that morning with the daytime high of a windy 32. I loaded it up with 5 large slabs of 2 year old white oak. I did not weigh the wood but I estimate the 5 slabs weighed roughly 70 lbs. Stove held 700+ degrees with the fan on for two or so hours before settling at 600. 13 hours later the stove top was still 250 degrees with no fan. It was 325 degrees at the 11 hour mark. Getting these burn times is all in the fuel load.