I have a MB C2D. If the battery is fully charged and I don't use the MB for 2-3 days (turned off, not sleeping!), when I next use it I get a "20 minutes until battery is charged" indication The 20 varies quite a bit. Is it normal to lose significant charge after 2-3 days of having the MB turned off? I know batteries do drain, but I always thought it would take weeks of being turned off to really matter.