That's about what I figure too. The weather guru's are saying highs in the 70's and lows in the low 50's for the next 2-3 weeks. My kind of weather. If I could control the weather, this is what it would be for most of the year. Last year we were burning by mid September. In, I believe it was 2010, we had frost Labor Day weekend.
Fired mine up last weekend, 9/20/14 it was 59° in the house that morning so I brought it up to 80° in about two hours!
