I think you will find that the life span of brass is highly dependent on your loading practices...I seldom load "hot" loads for my firearms unless that is the only accuracy node I can find...
While I have a bunch of brass from which to work, I generally use the same 100-200 pieces until it just won't hold a primer anymore...
Normally, my AR brass is turned over much sooner, just due to loss and replacement, but my bolt action brass is generally neck sized and annealed on a regular basis...
If I could find a decent tool that would allow me to retighten the primer pockets, I doubt if I would ever need to buy another piece of brass...I have 400 rounds of virgin Lake City .223 brass that has been sitting on the shelf for about three years, 1,000 rounds of 10mm and 500 rounds of 9mm virgin Starline pistol brass that is still in the original packages that I've had for over four years...