I never worried about it, because on a device that I use all the time, I figured that the extra time that spent trying to manage plugged/not plugged situations, wasn't worth the extra few months of life I may get from the battery. I don't believe that aggressive management of battery charge will give it substantially more life, so I just don't worry about it.
Also I spend a fair amount of time doing IT work "in the field", and so try to keep my battery topped off as much as possible, because I never know when I'm going to be away from an outlet for longer than normal.
My boss is a bit obsessive about the battery charge thing, trying to always let his devices run to almost empty before recharging. I kid you not, has to be at least 5 times now that I have showed up to do work that he requested for his laptop, only to find the thing shutting down due to low battery, and his charger is on a different floor, building, etc.
Anyways, my two cents' worth.
-Michael