Wow, a landlord who labels by date too? What made him start keeping track like that, did he get burned by a wrong part before?

Been there, done that, got the stiff neck.

Did you count the chainsaw and gas too? I ran a stove in my 900 square foot place for three years and the real number was way less than the guy at the stove shop told me. What killed me was the wood. First year I bought two cords at $280 each, then I figured out scrounging free stuff off Facebook and Craigslist saves a ton if you have a truck. I also stopped paying a sweep every year once I learned to do it myself with a $40 brush, that alone saved me $150 a season. My honest take is you still come out ahead, just not as far ahead as the sales pitch claims, and the comfort on cold nights is worth something you can't put on a spreadsheet.