Life of a MacBook Pro Battery

I do most of my computing on my trusty MacBook Pro. It's a power house fast enough to replace my old G5 powerPC, and it gives me the flexibility to take my work with me when I travel to a production location. It also acts as an external monitor when I have Adobe's On Location running. However, I've kept it plugged in most of the time. I'm not good at, and don't want to worry about checking the battery levels throughout the day. A year has gone by, and now my laptop just shuts down after a few minutes of use when it's not plugged in. It turns out it's a good idea to routinely "exercise" your battery, draining & charging it, so that this doesn't happen to you. Hopefully I can get my battery back into shape.