I believe that running the fan affects burn time and I see it affect the thermostat but I don’t understand how, being that the fan seems to be outside the firebox. I tam a week into a princess and the stove has exceeded my expectations. I am burning well seasoned dough fir and maple. I have had my heat pump turned to fan and it’s heating my 2500 sq ft rambler. There is an air intake above the stove, which helps. I am getting 15 plus hour burn times. These are amazing stoves.