French military ammo was loaded with berdan non corrosive primers it's shelf life is 40 years, but other military surplus ammo should be good for at least 100 if stored in a cool dry place preferably in air tight steel containers. I have shot some 1907 Krag 30-40 with no trouble, and thousands of rounds of British .303, and Turk 8mm from the late 1930's with no trouble either. If you open a container of very old smokeless ammo and you get a strong acid smell this will indicate the powder is turning bad, with a smaller batch pull a bullet, if you see brown crud were there should be powder, or anything that does not look like gunpowder it's bad. This will not detect dead primers of course, you will have to fire it for that. Black powder is good forever, you can even dry it out if it gets wet and use it, BP cartridges can last a long time and still fire.