I don't use my battery for my IBM ThinkPad T40. I simply charged it to it maximum capacity then removed it.
I'll also point out that the capacity of my battery has been cut in half during the approximately 5 - 6 months when my laptop (along with the battery) was plugged into the AC outlet. Technically speaking the battery should have electronics to prevent it from being overcharged and loose capacity like older NiCad rechargeable batteries. Therefore, I am guessing that heat killed my battery life since the battery would feel warm to the touch while connected to the laptop even with a full charge.