As long as it's been stored in sealed containers you should be good. Smell it first before using it. If it has a rotten egg smell, it needs to be disposed of.
I've got some shotshells from the 40's with paper hulls and they still shoot fine.
I gotta agree with Post #2. It all depends on how it's been stored. I have a terrible habit of buying a pound of a certain powder, trying it out, not being satisfied with how it produces and then storing it away in my cupboard for gunpowder. Some of it is indeed 20 years old, but every so often I might try that powder on another "brain-fart" that I have for reloading, just to see what it will do. Powder works fine after being stored in a dry area with no huge temperature fluctuations.