Actually, that turns out not to be the case.
Back in the 80's I was big into what we called then "Practical Pistol" and three-gun matches. I reloaded a lot of .45 and .223.
My attention got diverted, sold out of shooting and recently I purchased another AR. Digging around in what remained of my gun "stuff" I came across 30 rounds in stripper clips of some of that reloaded .223.
I figured, "What the hell" and took it to the range along with fresh factory stuff.
Could not tell the difference - it all fired with good accuracy and cycled fine. It had all been stored in the garage in a 50-cal ammo can (not a controlled environment) for 30-some-odd years.
And as far as I know, here in Texas there is no upper limit on the amount of ammo one can own (as a US citizen)
That is really not that much ammo for an avid shooter.
Personally I rather have fresh Ammo and dont shoot near that much.
But if 1 person shot 15 rounds every day for 5 years it would equal 27,375 rounds of ammo.