While it is certainly recommended that you have plenty of ammo on hand, if you are in a situation where you may be putting your life on the line, you should be using new-production ammo. Although properly-stored ammo will last for decades with little degradation, there's no way to tell how surplus ammo was stored. Often, the reason the ammo was surplussed in the first place was because it was left exposed to harsh conditions and can no longer be trusted for military use. Other surplus ammo is ammo that didn't meet required specifications and was sold off to reduce financial loss. In neither case should you bet your life on this ammo. Buy new-production ammo, test some of it in your rifles and then store it properly.