Mines open all the time throught the forced draft. I can get a 8 hour clean burn at night. I have a 35 foot masonary chimney, that had a bit of overdraft. I installed a baro and haven't had a bit of problems with the system. One thing to remember is they have alot of heating output. When heating 1000 square foot, it will throw you out of the home. They are made to burn when its cold. I would worry about a chimney fire by choking one down too much. You'll have to load it in smaller increments if you want to keep the heat down, if you load it to the gills for a long burn, expect too much heat. We have 2 temps in the home. 80 and 80. When its mild, I will only burn a few splits, and let the small coal bed kick in the heat. When its cold and windy then its a different story. I could get a 10 hour burn, but it wouldn't keep the house up to temp at night. Why waste heat, lower the burntimes a little and get more btus in the home. It takes some time to find a sweet spot, thats all.