I've got about 4 quarts of tower hobbies 20% fuel from 2001 and it works just fine, no issues at all. I bought 2 gallons back then and have since bought various quarts of other stuff. Anyhow they were wrapped in newspaper and stored in a box on my basement shelf. They never saw light until ready to use and they worked just as good as day 1. I've been using it to mix with 30% blue thunder fuel lately to make it go further and have not had any issues so far. I was under the impression that after a year or so it went bad, but nearly 9 years later its still working just fine. I haven't had to retune my engine or anything, it just works. So at least in my experience as long as its sealed and doesn't see any light it should stay fresh for quite some time.