A bit of a tangent but seeing guys say the same wrong thing repeatedly is a bit irritating.
Powder begins deteriorating as soon as it is made. The powder sitting properly stored in your home or shop is deteriorating right now, it's just doing it extremely slowly thanks to the addition of stabilizers. Heat is the number one cause of deterioration to the point of actual breakdown of the product.
YOU'RE splitting one minor hair off a gnat's butt.
Powder will deteriorate for all sorts of reasons, even if stored properly and of relatively recent manufacture.
Ganderite could explain this much better than I can.