If tire manufacturers are reading these forums they must be throwing parties over the paranoia here. Every time someone causes panic and posts that you must change tires at 5 years, the tire companies wallets get fatter, for no valid reason!
If you bought your tires new and have taken reasonable care of them, 5 years is a simple waste of money. If your live in such fear of a blow-out, as to throw $3k+ out the window for no reason, maybe you're in the wrong hobby. I would hate to be driving down the road in fear, every time I got behind the wheel.