It doesn't have to be kept refrigerated. A properly cleaned, sanitized, transferred, and purged keg will last just as long as a bottle of beer. Both bottles and kegs will last longer if refrigerated, but will still last for a certain length of time, a lot depends on style of beer, if kept unrefrigerated. One thing to note, though, is that kegs do a better job of blocking out light, which is a good thing for beer.