You're forgiven.
If I wasn't so damned lazy I would've hunted down the info before my first post instead of just relating a story I'd heard.
The obvious conclusion is that, at the time of that article's writing, there were still 350k WWII vintage rounds floating around.
Which means we STILL haven't burned through all the WWII stuff.
Moral of the story: ammo, when properly stored, can last a LONG time.