I purchased my Regency Insert in 2008. So I have been burning with it for 3 years. My gasket on the door looks a little flat. Through the years I have ajusted the door to make it fit tighter when I felt the door was feeling loose. On average how often do you replace the gasket. I did the dollar bill test and it seems snug all the way around the door. In one spot I could pull the dollar out if I pull a little bit more. How hard should you have to pull on the dollar bill and how often do you replace the gasket.