I've kept some old powder in neat old containers my brother used to use in the 70s but I don't feel like I need to use it. I was always taught to smell the old stuff before using it because it smells acidic when it starts to deteriorate and go bad.

I figure that new powder is cheap enough that I don't need to use old stuff when I'm not sure. I do a lot of precision loading for accuracy and want reliable ignition throughout.

But, for shot shells that aren't that critical- go ahead and load some, then test it out. It won't harm you if it is bad. Might just not explode or give a hang fire.

I like taking old stuff and lighting it to watch it burn. But, that's the pyro in me!