Since I recently started reloading I don't have large quantities of ammo on hand at any one time. I load a hundred rounds, go shoot 'em, load a hundred more, go shoot 'em...
But it's summer, and I'm fairly busy with other things. This winter, when I'm stuck indoors, I expect to develop a storage problem. I've stored ammo in a Playmate picnic cooler which seemed to work pretty well.