Since I am also penurious, I pecked around a bit (I am waiting for a proposal edit and have a few minutes).
This was the best link I could find:
Tires: New tire not really new, Tire Storage, Tire Age
I recently bought a set of new tires. After they were mounted and balanced, I noticed that three were manufactured in 2009, but one was not; it was manufactured in 2008 (the 25th week; the last 4 digits of the DOT code were 2508). In other words, this tire was manufactured more than one year ago. Is this a concern? Should I go back to the store and request another, newer tire?
Thanks for your advice.
ANSWER: Kenneth,
This is not a concern.
Tires can be considered to be "new" for up to 3 years with no other consideration. Tires that have been properly stored have a shelf life up to 5 years. If extraordinary storage conditions are used (like hermetically sealed in a bag full of nitrogen) - well, no one's done any research on the subject, but it must be a long, long time.