I'm a classic, hard-core "introvert" in Meyers-Briggs type indicator parlance (an INTJ, if it do ya). If you're familiar with their definition of Introverted, it has more to do with how you process information than with how outgoing your personality seems to others. For me, it means that I need time to process information, and when you couple my Introversion with the other aspects of my type (iNtuitive, Thinking, and Judging) it means I like to get lots of data in, then I use my intuitive bias to see patterns, make connections, and form hard conclusions.
Lisa's post sparked one of those "connections" for me, as I realized that it's important for me as an introvert is to deliberately build time into my schedule to recharge my batteries. You see, Introverts find lots of social stimulation to be a bit draining at times, and need some down time to process the information they've accumulated - this process is where we become energized.
So, while I think it's important to know what size battery you have, I think it's even more important to know what to do to make sure you get a full charge now and then.
For me, it's typically activities that allow me to gather new information without feeling the pressure to process it immediately. That means things like reading, watching the Discovery channel (or the History channel or somthing like that), reading blogs, listening to talk radio and audio books, and that sort of thing. It often involves quiet time alone.
If you're an extrovert, your recharge might look different - it may involve some social interaction, talking with someone into the wee hours, having a good debate, or just going to a party and socializing.
In any case, build in some time to recharge your batteries - it's no fun having them run down when you really need them.