Well...to answer my own question, I fired the old .410 shells this morning and they worked fine.
Have a new Taurus Judge that shoots .410/45 Colt. This is more of an ammo question, but hope someone here knows the answer. Have a box of .410 shells that are about 20 years old. Safe to shoot? Or does shotgun ammo expire after a while?
Well...to answer my own question, I fired the old .410 shells this morning and they worked fine.
For whatever it's worth, I've recently fired .45 ACP rounds that I handloaded more than 20 years ago, and they worked exactly as they should.
I have also fired both .45 ACP and .30-'06 rounds that had been manufactured and issued during the middle of WW2 (67 years ago), and they worked properly too.
It's all in how the ammunition has been stored. "Cool and dry" is the way to go.