I have primers that have been stored in a cupboard in the house for 25 to 30 years, would they still be good to use?

Chuck

Mine of similar age perform flawlessly. I'll be using some of 1973 vintage on a late-season elk hunt in a couple of weeks, so, as you can see, I have full confidence in them.

Of course, your conditions of storage could vary from mine. Simply use a few dozen in some practice or firforming loads to determine if they are still performing as new.

Primers are one of mans greatest inventions and it is extremely rare for one to fail even very old ones. The only primer I have ever seen fail have no compound in the cup. That had to have happened in the production process. Keep them cool and dry, they will last far longer than you and I will. I have seen primers soaked in oil still go off when struck by the firing pin. Never think for one second any contaminated primer is a dud, you may end up seriously injured. Always treat them as live and dangerous when disposing of them even if one should not go off when struck by the firing pin.