I would add that it's probably a good idea before firing any to pop one open and see the condition of the shot. If they were not stored properly, the shot may have whitish oxide on it. This could indicate that instead of a couple hundred individual pellets going down the bore, you'd get one or two masses, i.e., something approximating a slug or slugs.
If the shot looks new, you're probably good.
I did this with a box-less-one-round of #5 16ga W-W Super Speed papers I got at a gun show and ... they were fine. I recrimped the one I opened and I'm good to go.
