It is obvious that no one here can factually say when ammunition is unsafe to shoot. During the current .22 lr insanity I began shooting ammo from cans that have not been opened in 30-40 years, had a few misfires but new ammo will give that. Also shot a coffee can full of 1913 Frankfort Arsenal .45 auto (that's 100 years ago folks) with only one FTF. Posters have previously noted ammo should be correctly stored and as a result will have an exceptional shelf life.