Its not good for any battery to discharge and my Nav V always gradually discharges when not used for a month. Switching off doesn't help, cos its not fully off and it discharges quickly. Full power down, by holding the on button and selecting 'Turn Off', is massive better, but the unit still discharges. Somewhere I read to disconnect the battery during long periods off but that's an arduous screw driver task. Does yours discharge and do you worry about it 

