Store your powder in the container it came in and keep it away from moisture sources, and it will be good for many years to come. Although a friend of mine was over the other day shooting and having trouble with his Pyrodex. His rifle was really being stubborn about going off regular, so I suggested he shoot some of my Goex and the rifle tuned right it. The powder had somehow gone bad.

I have had powder around the house for 6 years and it shot off fine.