I still have a couple full cans of Meteor powder. As I recall it was a decent performer, bought several pounds of it years ago. Shot up most of it, had two cans left in my stash. Figure so long as it stays dry it will be good for years to come.
I've actually collected a few older cans of various brands. Some were full, some empty, some partials. Mostly picked up here and there, at shows, flea markets and yard sales. Some of the old cans have scary high prices on them at the collector shows, I tend to avoid those. Like the artwork but only buy when the price is right. I have used odd batches of old powder but I always spread it out on a white fiber board and inspect for any signs of contamination. If it checks out okay back in the can it goes for use, anything suspicious goes into the burn pile.