Avgas contains Tetra Ethyl Lead (TEL) and other additives to keep it "longer from breaking down and causing "Gum". Costs more than vehicle gas, but much better. I have a private airport about 10 miles away and I have the combination to the gate and pumps. I also put in Sta BiI in.
I have my Avgas 2+ years with no problem. I usually start rotating barrels out between 2-3 years (change out one every year -ongoing) with mixing 5 gal in a every tank of gas in my truck and then buying a new amount.. Use it in all my chainsaws, mowers. Works great and there is no Ethanol to degrade fuel lines and gaskets. I don't have to worry about leaving gas in my saws, generator, motors for extended times.