When it comes to ammunition, there's only two times when you can have too much: When you're moving, and when you're trying to swim with it (and yes, I've experienced the moving part...)
American Eagle's 120-round ammo can makes keeping ammo on hand easier, and even a little fun. The miniature ammo can holds 120 rounds of the company's excellent XM193 (55-grain FMJ 5.56 NATO ammunition) in a plastic box that's both durable and stackable. It's easy to keep several hundred rounds on hand without cardboard boxes falling apart or metal cans scratching up the hardwood floor (again, not that I've ever done THAT...)
Best of all, it's in an amount that works with 20-, 30-, 40-, and even the SureFire 60-round magazines!