currently running 2 Michelin Pros (of 5 purchased in '97). Both on the front wheels of my 2 most used bikes over the past 1 1/2 years - the one on the softride is at 4K and still rollin. The one on the Colnago is at 3.5 K and rollin. Have 1 left and waiting...
On the Colnago, at the rear, I replaced a Specialized Comp purchased in '90 (one of 3 puchased on sale) , this past thanksgiving - it had well over 3.3K miles. Not bad for a very light racing level clincher.

Just purchased some Contis and Vredesteins from a LBS that had them hanging around for about 3 years, these will be my tires for this year. I also bought a BUNCH of Vredestein Fortezzas and Volantes (on sale) that will be put into the tire closet for the next 3 years before being used.
My preference is tires stored for at least 3-4 years before use; not just for increased mileage but mostly for the clearly 'finer' ride characteristics that they exhibit. This seems to hold true even for the lesser 'training' grade of tire. The storage key is to find a place with even temps, not high or low; neither high or low humidity - a closet seems to work just fine. Most retail stores are quite good 'storage' places as well, since they usually are very even in temp and humidity. I 'scavenge' for old stock a LBS is looking to move and often marks down.
If you;re doing a lot of miles, it really pays both in mileage and performance to have a couple of years supply 'aging' in a closet. At least if you think you're gonna be ridin 3 years down the line.
same, same for sewups - I have some Vittorias and Clements that are now about 5 - 6 yrs old and ready to ride.