For me, it depends on whether or not the thread is purely informational or is a discussion of opinions and observations. If you are looking for a specific piece of information it would be best to look it up on old threads. If you want to have a discussion, doing so with a five year old thread just doesn't work. And I've seen old-time Mudcatters cattily telling folks that we've discussed that all before and everyone always says the same thing. I find this sort of dumb when I'm in a thread with a couple of other people who were not part of any of the previous discussions. It's clear that the newer people did not say anything in the previous discussion.