The past 40 years have probably not been as hard on your primers as they have been on me. If they look good, (perhaps smell good?), load some in otherwise empty brass and see how they compare as to report and flash with new primers. Primers can be dangerous, so carefully.
I still use 50 year old Herter's primers. I have never had a misfire with one. I have gotten better groups with identical loads using 35 yo BR2 primers (maybe 0.20 inch) in a couple of rifles. I am guessing I would have gotten best loads with those primers anyway.
During quarantine I have loaded a ton of comparative loads using the old Herter's vs. other brands and even some brand new primers. It will probably take me a year or better to give a comprehensive comparison. I am down to less than 2K of them, and am not looking forward to having to buy all new.
In 1968, I bought 20,000 old Western, small pistol with the round crown in wooden trays. I used the last of them in about 1997 in K-Hornets and Fireballs. Never a problem but I had to modify the primer seater for the round crown.
Some new shooters may have never seen a round-crown primer-
I was given a box of remington small pistol primers, estimated to be from ~ 1965, a half doz years ago. some were rusty, so I threw them out. Of the remainder, they were about 20% duds. The rest has varying brisance.
Certainly don't want to use them as my self-defense loads!
If a primer has been exposed to moisture they are likely not at "peak" performance. Oils don't seem to cause problems although I have not used them in my guns that way. I made some igniters using primers, ball powder and oil so I could compress the powder and even after sitting saturated in oil for several days they all fired just fine. They did a fine job of igniting the material I was working with.
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