If, whatever you do has a catastrophic effect on your battery & you kill it
They are all of £13'ish for a new one, so its not really a biggie either way........
Me I part charge my gizmo's as & when, then occasionally (Like once a year) run em' right out, then charge em' fully......... It was something I read somewhere once.... Batteries it would appear die of boredom mainly & certainly do have a useful shelf life, quite what it is, is a secret that if Sony told you they would have to kill you.
http://www.ultimate-mobiles.co.uk/er...-mah___489.htm