Inspect them carefully. It depends a lot on conditions they were kept in. Modern day ammo generally has a more than exceptional shelf life. most depends on storage. I'd be wary of any shotgun shells that exhibit rust anywhere. With proper storage, 30 year old brass cased ammo should be good to go depending. "Flaky" stuff, I'd beware of. If it exhibits any type of corrosion, I wouldn't use it. 80's factory rounds? Should be no problem. Just inspect them from box to box to be sure.