I'm the same way,5 years on a can,all gone now. it shot just as good the last load as the first.
I have now gone to pellets.I keep it all in a box in the case.

I would say as long as it is dry,it should be ok.

I am not a hunter I am a whitetail population reduction specialest

remember keep your back to the sun, your knife sharp, and your powder dry.