Heat is a major cause of battery degradation, partially why I don't agree with constantly charging/discharging since it causes more heat.

Keep your laptop cool, perhaps even consider battery saving options while plugged in if you find it is generating too much heat.

Edit: A running laptop will cause heat, so shut it off when not using it. A plugged in laptop shouldn't create much more heat than a laptop running on battery power, if anything, the battery should be cooler when plugged in and fully charged (assumption made).