Keeping a battery at 100% while plugged in can degrade its lifespan. Many notifiers will alert you when it's time to unplug.
Track your battery's "wear level," temperature, and charge cycles to know when it's time for a replacement. battery notifier download
This is a powerful, free replacement for the standard Windows battery icon. It allows you to toggle power schemes instantly and set highly specific notification triggers. Keeping a battery at 100% while plugged in