I have been doing some reading on the li-ion batteries. Lots of great info on them, but I'm a bit confused on one point. Some people say to leave them discharged if you are not going to use them for a while. (No one say how long a while is) Others say to keep them charged up. Some even go so far as to say you should charge your battery as soon as you are done shooting, even if the battery is not completely discharged. They say you will get better battery life. So, which one is it?
The most time I would go without using my batteries is about a week to three weeks at most. If I didn’t use a battery for say a year, would it be better to store it charged or discharged?

Thanks for your input on this.

All the things around Li-Ion batteries look like a black magic to me. I recall reading somewhere that Sony officially recommends fully charge betteries before putting them to storage. However, Sony batteries differ form others in their internal structure, so it's hard to tell how this applies to the others.
In my experience the batteries become unusable in a year or two, no matter how you store them.

I recently bought a CGA-DU21 battery for my gs100. It came along with an instruction sheet of how to get the best out of it.

The sheet is not in front of me right now, but, some points that I recollect:

1. Store them discharged.
2. For long term storage Fully charge the battery, then discharge the battery by using it in the cam until the cam switches off on its own.
3.Battery will 'die' if not used for extended periods.
4. Fully charge and discharge at least once in 6 months.

I dont have a scanner, else I would have scanned the sheet and uploaded it.

Thanks for the information guys!