If stored properly. If it is in conditions that you live in, it should keep fine. Well, if you have a super humid basement, I would use air tight containers and maybe dessicant. Or if you do mechanic work, keep it away from petro odors/fluids... Otherwise, long long time. I don't think I have ever fired WW I ammo, but I fired a bunch of 7x57 round nosed dated in the 1920s. No problems. No doubt, you have heard that oils will deactivate primers, even vapors if strong... The one batch of powder that "went bad" was, per NRA Rifleman, made during late WW II and several "wash" steps were skipped to get it into use against the enemies of USA. This left manufacturing acids that caused it to deteriorate when it got into surplus after the war. If the smell is normal, like ether/starting fluid, or acetone/ finger nail polish remover; no problems. The scent to avoid is like vinegar/ "acidic." luck