I have rifle and shotgun ammo that is 30-50 years old. Recently I fired a .270 round and a 12 ga round that had a little green "surface" corrosion on the brass. Polished it off with a little steel wool, and it looked fine. Both chambered and shot fine, but both split the brass where the corrosion was. So as long as there is no corrosion of the brass, I would not be concerned. But if there is, I would discard the rounds.