Currently looking at a Bosche SX/400kwh bike but am thinking about complementing with a range extender. However I have read that lithium battery systems in general degrade if they are in storage most of the time and not being used. If a range extender is only being used once or twice a year (meaning only charging and discharging once or twice a year) is that going to be a concern where it would need an early replacement after 4 or 5 years?