A few years back, I bought a Vermont Castings Encore Flexburn stove. It was not my first choice, but it was the best stove I could buy on Amazon as one of my clients had given me a few thousand dollars in Amazon gift cards. First, I have to say I'm happy with it - it can keep my whole house warm even when it gets down to -15. In the Winter this stove is pretty much going all day, every day. I live on 15 acres of wooded property and have much more Oak, Ash, Black Cherry and other woods that I can process. In its specs, Vermont Castings says this stove has a 12 hour burn time and I see other stoves advertise even longer burn times.
But if I pack this stove full of perfectly cut, seasoned Oak with the catalyst hot and a glowing bed of coals, I probably could barely get 6-8 hours of actual "burn time" where there's flames in the stove. Yet it will easily stay fairly hot for 10-12 hours, but at a slowly declining rate. So if I stabilize the burn at 425 surface temperature, it's fairly likely the surface temp will still be at close to 400 when I wake up 8 hours later, yet most of the wood will be gone, with just a layer of hot coals left. Also, I've had enough hot coals last 18 hours to light another fire without kindling,
So what is "burn time" - is it the time from when you load the stove for a long burn until the surface temp drops to the point where you would reload it again? Or is it when the wood is gone and the flame is out?