The way I see it is time management: life is short, do you want to spend most of it dealing with people or things? for me it's "things", because they have a higher signal/noise ratio.
I'd say that "it's probably best to be somewhere in the middle, so that you're neither worn out by social situations or bored by spending time alone" but there's probably enough self-aggrandisement in this thread already.
As for not being able to change however, I don't believe that's set in stone. I took the test about 7 years ago and since then I feel like I'm more like 65%i/35%e. The whole idea of charging however is strange. Though I felt back before the test that i could only recharge at home, alone. At one point while i was the most social I felt as if I had to charge at home, then go out to recharge to balance it out. The brain is a very strange thing.
I'm very much an introvert, but over the years, I've learned that networking is a critical part of being successful in any business endeavor, and it is nearly impossible to network following typical introvert patterns. As a result, I will go up to a group standing around at a social event, throw out my hand, and say "Hi, I'm Travis. What's your name?" even though I hate every second of it (and, given the sieve my brain is when it comes to names, I will likely forget before we are done talking :/).
Given that, I don't believe for an instant that I understand being an extrovert. My wife is the prototypical extrovert. She will have life-long friends within minutes of entering a room full of people she's never met before. I will never understand how she does it, but more importantly, I will never understand why she does it.
My real point is that anyone who believes they KNOW how anyone else thinks is wrong. It's a very egotistical thought to have that you know so well what another person thinks or feels.
Here's what I think: as a young kid, you get exposed to things that shape your attitude. If your early experiences are negative in social settings, perhaps you grow up to be introverted. But what happened first - your negative experiences, or an attitude that pre-disposed you towards negative social experiences? Can little little kids have attitudes like that? Hard to day - how do we really know?
I don't care what physical science has to say on it regarding brain maturity, neuro-pathways, etc - unless we can communicate with infants, we don't know if they have pre-disposed attitudes or thoughts.
http://www.ribbonfarm.com/2009/08/06/on-seeing-like-a-cat/
In principle, it seems possible to have more interest in things than people ("think like a cat") but still get energized by people when you're with them (or, continue thinking like a cat when you're around them and explore how you can subtly direct social interactions or explain the behavior of others using simple theories like status preservation).
If this is how you think extroverts are, then I would suggest that you don't understand very well how extroverts think.
As someone who spent his youth as an introvert and later discovered the joys of extroversion, introversion seems like a suffocating, lonely, and stunted existence. Do those years mean I understand how introverts think? Of course not. Introverts obviously don't think their lives are lonely or stunted. Instead, I have to view others' choices with humility and accept that their thinking will always be alien to me.
Someone told me Friday "if there is nothing inside of you, of course you will try to focus on showing your outside. That is all you have.".
Common misconception about introversion vs extraversion: that it always manifests in interactions with other people. The reality is that they define how you deal with the outer world. For instance, riding a roller coaster is an extraverted activity, even if you go alone. Staying home and reading a book is an introverted activity even if you invite someone else to read with you.
When you say you like "things", that's still an extraverted attitude. Things still exist in the outer world. The real question is "Do you prefer the outer world or your inner world?" This is the question that helped me realize that I'm an (unfocused, non-goal-oriented) extravert.