I would like to suggest, in case you have not yet, if you constantly keep your laptop plugged in, there is a setting that will keep the battery at 80%. Most battery degradation, from what little I understand about lithium batteries, happens from 80-100%. A lot of phones, and most modern laptops, will bypass the battery for the most part when it's plugged in. If you're going on a trip or something, you can temporarily boost it to 100%.
Now all batteries will degrade over time no matter what, and even when plugged in, you will have some very limited battery drain (and recharge). But the degradation should be pretty minimal, as long as the room you keep it in is about regular room temperature (70-75 degrees F).
