I also have a decent selection of black powder and I knew a man in Illinois,now deceased that collected powder cans,the older the better and he had a container that was from a family that traced it to the Revolutionary War and it was still good.I still have a can of DuPont I bought from Wes Kindig at Friendship in 1956 and it is still good.
On a related subject,does anyone have any data on the shelf life of percussion caps??
I have a few Remington #12's in the pretty little 100 shot containers with the green band
that I bought from E.M.Farris in 1964.At that time they were $4.50 per 1000.
Bob Roller