Don, I was given some old K&B {I think} fuel that was stored under A bench for well over 15 years and the stuff worked just fine. About 10 years ago I found A couple of pint cans of Thimbuldrom {spelling} fuel that I had boxed up with my Prop Rod when I was A kid. That fuel was over 37 years old, worked just great in my 1/2 A glider engine.
Unless the fuel gets water in it the stuff doesn't break down. That 1/2A fuel had moved from So. Cal. to the mountains before I found it again so it traveled A long road before it got used!!