battery charging

Well I usually shoot till the camera batteries die and then charge them. But I was wondering if need to do that, or can I start charging them when they get down to like a quarter left of charge? Without causing them to shorten their life expectancy between charges?
Thanks for any advice that comes my way.
Grady

Lithium Ion batteries aren't like NiCd batteries - you don't have to run them flat, and in fact running them flat all the time can actually hurt their life expectancy. Maybe run them flat avery so often, but there's no need to make it your standard practice. Just recharge 'em when you have the chance.

Thanks Jon, just wasnt sure about that.
Grady

As Jon said,, no need to run them flat..

I have two cameras both with grips and six batteries which are all interchangable.. I run two batteries in each camera.. I will rotate my batteries regularly so they all get equal usage.. I will often recharge my batteries to keep them topped up..

I have two batteries (non Canon) which are approaching four years old and still work like new..

Thanks yogestee, Im planning on buying 2 more batteries in the future so I always have a set that is charged, just havent done that yet. Thanks for all the replies and advice.
Grady