Me to, well so far, we had a cold snap a few weeks back and my burn time took a big drop even though I didn't adjust the setting. I can blame this on two distinct possibilities. 1)The draft is stronger which sucks more air into the firebox through the set orifice in the intake damper. 2) The stat is doing what it is supposed to and regulate the combustion to maintain a steady temp in the room. I'm leaning towards #1 but it is amazing how the room temp holds steady and the wood just goes away faster all without user input. Probably a combination of both.