Havent timed the flame part of the burn cycle. but I have gotten a good bed of coals for relighting the next load a few times at 10 hours, but I regularly get 8 to 9 hour cycles out of the stove, its rated for 12 hour which I think I could get if I had big chunks of good dry oak. But I split all my wood smaller so it will dry out faster, like 6" to 7" approx diameter or smaller. I would like to have more 8" approximate diameter or larger splits. Big splits need to be good and seasoned, which i say would take a good 3 years cut split and stacked. I will tell you this the reason for those good secondary flames is that the wood was stacked high on an already hot bed of coals. The small space up above creates a little super heated burn space for good secondaries. Its all about the heat and small spaces are kept hotter than larger spaces like a half loaded stove. Putting good dry wood on a large bed of hot coals means fast off gasing and lots of that gas floating up into the top of the stove to be reburnt by the secondary air tubes feeding air to it. The funny colored flames is the camera not the flames doing that. Good Seasoned higher Btu wood like say a oak or hickory gives alot better secondaries than lesser wood.