Most ammo, stored in a dry place that is reasonably cool (below 90 degrees F) will be in excellent shape for at least 50 years. I try to use up all my old ammo before that time frame. I have shot lots of ammo that is 50-60 years old, and it mostly works just fine. The problems arise from ammo that has been exposed to water or, worse, oil.
The NRA tested ammunition that was a bit over a hundred years old, and it generally worked very well.
If you are shooting old, questionable ammo, you do not have to worry about cartridges being overpressure and blowing your gun up (unless the cartridges are unknown reloads). What you have to worry about are squib rounds that stick a bullet in your barrel (shoot the next round without removing the obstruction and blow the gun up), hang fires that go click...boom, and misfires that do not work at all.
I do not worry about shooting old ammo, as long as it is in a situation that is not critical. I shot a bunch of 12 gauge that had gotten soaked and then dried, hunting dove. It nearly all was satisfactory, but I did get a few misfires and one hangfire. You just have to be aware, and do not shoot another shot until you check your bore, after getting a misfire or squib load.
Thanks. I’d heard that but still.