At my "main" message boards (
http://www.arstechnica.com ) we recently stumbled across a guy who has only posted 8 times in three years. 2 in one thread, 3 in another, and then 3 other times. Most of that content was invaluable information appreciated by all viewers.
I referenced one of his posts 9 months after he had typed it and within a few hours he stepped in to the new thread to update his old info, and to say thanks for citing him.
The moral of the story is that people are watching you, and when you need them, they will be there to help.
Just because they don't have to say something about everything does not mean you want to make it harder to hear what they have to offer.