Are you asking if there is something that you can do to help extend the time between charges, or to extend the lifetime of the battery?
Simple answer to your last question is, it will extend the life cycle of the battery if you leave it to die completely before charging it at least once every 14 days.
@wolfeking: Actually I'd like both, are the problems so different in solving?
From what I understand, if I were more interested in the lifetime of the battery, I should first check whether my battery is lithium or not. If it is then if I empty it before I charge it I'll actually damage it. Is that correct?
About changing the battery, I've heard that it costs more to get a new one than getting a new netbook, is that true?