Key to buying "sight unseen" is not being able to verify the "date code" to know just how fresh the tire is. Use the Self Help or Search Tab and you will find links on how to read 'em, especially if you are buying "off the shelf" and your local shop! Best to be safe than sorry...:s
http://www.hdtimeline.com/brakes_tires_and_wheels/1587-tires_deciphering_the_codes.html