I have some primers so old that they are still mercuric I think, mfg in the 1930's. I do not load them, but occasionally I set a few off just to see if they still function. They were in with a bunch of bullets in old tobacco tins labeled as having been cast between 1927 and 1931.
Most of the primers and loaded ammo I am shooting up now were loaded in the early to mid '90s, and I have yet to have jacketed loads fail. Some cast however have , and I attribute that to the lube seeping into the powder or degrading the primer. Most still go bang, but a few in each box have failed. This is on 20+ year old cast loads.