Do Li-Ion rechargeable batteries lose power when not in use?

I'm thinking of getting a spare battery for my digital camera...I'll leave it charged, but if I don't use it for a week, for example, will the charge decrease? thanks.

My D100's batteries (with MB-D100) last for weeks without charging and after 500 or so exposures. My D200 uses power faster, but still the batteries last much longer than what I keep hearing here.

My guess is that other photographers don't use very good power management ... Having their LCD monitors turn on after every shot and stay on for long periods of time after the image is captured.

I keep mine off. Only look at it if I am shooting in an unusual lighting situation.

In any case, there are at this time no better batteries available for digital cameras

it will but not much in only a week

a

it will most certainly lose its charge conciderably ina wekk or two

Yes.