I believe that the Hodgdon Powder Company started by selling WWII surplus bulk powder stored in boxcars for 25+/- years. They re-packaged it and it was about as good as the day it was made. It probably wasn't exposed to extreme heat, however.
I have a few cans of powder that I bought more than 25 years ago and it's still good, but it's been stored in cool, dry conditions.
People are like rifles. Some are tried and true, having great eyes, personality, and fun to be with. Others never seem to hit the mark with you. Still others go off half-cocked. Still, it's nice to know most of them.