When I was at Sun n Fun this year buying a couple cases of Aeroshell from the Shell booth, I asked what the shelf life was. Shell told me 4 years after which it would have to be retested. My engine and plane are too important to me questionable oil in it and I would never feel comfortable trying to use it regardless of the deal I got. For me, we're talking lawn mower oil, maybe. Or, flush out oil. But, thats just me. Call Shell or visit their website..
Here is some info from their web site about shelf life and re testing..
http://s01.static-shell.com/content/...-shelflife.pdf