While I was getting ready for the storm, I took some time to clean out my ammo locker. I took some old 9mm rounds down to the range for a little practice. I took the Beretta with me. The Beretta did what it usually does. It hit the steel targets with boring regularity. I shot some stubby lead reloads, Cor Bon 115 and 124 grain +P+ loads. They really made the steel ring, and were very accurate. I also shot some CCI Blazer, Speer Lawman, and some old Federal Eagle 115 grain loads. The magazines are nearly worn out. It needs new mags, badly. But it still hasn't had any malfunctions, other than two failures to lock the slide back. The followers are all chewed up. I also practiced drawing and engaging multiples at thirty feet, from behind the wheel of a vehicle. A great way to take a break.
I wouldn't keep ammo more than a couple of years. About once a year I replace all my self defence ammo for new. If I have any ammo more than two years, I'll shoot the old and replace it with new. But I've seen ammo that is close to fifty years old fire without problems. I wouldn't want to trust my life to it though. Plus, newer ammo has the latest technology. Ammo from the early 80s would probably be inferior to todays ammo. Quality ammo is important. But if you're like me, you shoot it all off, way before it gets old. Good hits is the most important thing in a gunfight. Learning tactics and good techniques helps. I've went to several shooting schools (law enforcement schools) and good instruction makes a lot of difference.
I have a mint condition Savage Arms model 99 in .300 Savage. My dad bought it about fifty years ago with a couple of boxes of 30-30, and .300 Savage. The .300 Savage stuff is older than I am, but I have not experienced any problems. If the ammo is stored properly, it should last a long time.