Why is it when my Karma sits in the cradle overnight I pull it off and it's 100% charged but when it sits there for 3-5 days on but not doing anything I pull it off and it's 80% charged? This hasn't caused any grief, I'm just curious if it's by design or not.

Also, I recently saw an article about an anti-iPod campaign because it has a non-replacable battery with an 18 month life span. Is there any idea what the life span of the Karma battery is or if it's user-replacable?