I never let gas sit in carb after even a short run. I also pull the plug after each use, clean it and a quick squirt of penetrating oil down the cylinder. Gas is drained out of tank if going to sit for more than a few weeks (used elsewhere) and the the tank is cleaned as well the petcock/filter. Carb cleaned every season, air filter/oil every 3 or so trips depending on use. If I have a plug looking a bit dirty, its tossed and new one installed. Never run gas if sat more than a month or so especially with mix in it. I have ran 32-1 but usually bout 40-1 depending either mountains or desert.