Just find someplace to store it besides your basement or your garage. Store it in an environment where the temperature and humidity are controlled. All of mine is stored in a spare bedroom closet. How you manufacture the ammo is not going to have much effect of shelf life. How you store it will. Steel GI ammo cans work very well as long as the rubber gasket in the lid is not torn or distorted. I have used the GI cans for twenty years or more and never had any problems with them. Humidity is not going to get past the primer or bullet even if left in the open. Submerging it in water might. Consider all of the tons of ammo used in the Pacific theatre in WWII. It suffered from corrosion but still fired just fine (if it chambered and extracted.)