Walmart has plastic ammo boxes that seal up tight for only $10. I found the best value. Leave it in the boxes and put it in.
Storage has a lot to do to where they are stored. Keep temp consist and and dry. Import stuff comes in sealed cans if you want to stock up.
I am old and still have ammo I bought 40 years ago that work fine. Got some WW2 ammo that still work great too.