I have 200 rounds loaded up in 8 mags for long term storage with because the pressure of the spring and rounds can wear on the lips of the mags and potentially crack them.
I know a guy that has 1k for his AR all on stripper clips in a ammo can with a clip guide duct taped to the top of the can 20 thirty rounders ready to be loaded. He also keeps 8 30 rounders loaded with 20 rounds in a molle rig just in case of zombies.