RE: "expiration date" for shotgun slugs?
I make my living in the sales industry, selling guns, ammo and the related stuff. Our shop does well, times are good.
I would love to find the wonderful ammo company sales rep who started the rumor that ammunition has a shelf life such as milk, cheese and AA batteries.
We honestly have people come by the shop with coffee cans full of 12 ga shells, that have never seen the light of day. Apparently, they think we are an ammo dump...well...if they are still good, we will take them, and shoot them ourselves! No matter how much we try and tell people that these shells are still very functional, they just refuse to believe us! Well...better we shoot them then they thrown them in the trash.
Shells only go "bad" when the brass rusts real bad, or if you get them wet. Most modern shells are waterproof.
As said, those slugs of yours are good to go.