This is a pretty interesting article on new tires that have been sitting on the shelf for years. This is probably a little blown out of proportion, but basically true. Michelin told me a while back that a tire has a 10 year "use" span, and 6 year shelf life.
Considering the rarity of some tire sizes for our Cobras, this may be worth taking a look at.
http://abcnews.go.com/Video/playerIndex?id=4826897