Great page, thanks for archiving all of the information about your system, with great pictures too. I'm going to send it to a couple of friends.
I was thinking about your payback and figured it was around 24 years, but more like 38-40 years when you consider replacement costs. As you said you don't do it to save money and this page helps show you that you can't quite put a price on generating your own power.
And most hobbies don't pay for themselves at all!