As has been stated so well ... I can't really advise you. I do know that this site has been an incredible resource for me and helped fuel my GPN fanship. And I am a relative newcomer here.... for those that have been around since the beginning it must mean a whole lot. I understand where you are coming from, I had to make some similar decisions (and my activity there wasn't near as detailed and thorough as TIS) because it got to feeling like a "job". I have one of those and sure didn't need another, especially one that didn't pay anything.
I would hope that if you shut it down that you could still leave it the archived material around... it chronicles the history of this band that we all love so much. I wish that there was more activity/interaction here and on the gpn forum. 
Thanks for all the work. It has become part of my daily routine, a part that helps me unwind from the daily grind of making a living and all that goes with it.
In the meantime.....