I'm a newbie to the world of iPods (let alone the fact that this is my first Macintosh product ever). I love my shuffle, no doubt about it. But what's with all the disclaimers about the battery having a limited life cycle?? And Apple's webpage dedicated to it? http://www.apple.com/batteries/ So I shouldn't leave the shuffle plugged in? I should keep using it until it's really low, THEN charge it? Knowing that the battery is technically irreplaceable, this has me somewhat concerned. Any input is greatly appreciated. Thanks!