Very little. If I think of a topic i'm curious about, I do a quick search on the forum, those related threads pop up.. and voila, the trick, she is done.
And certain topics and threads are ageless; they are just as relevant today as they were 3 weeks or even 3 years ago, and many get lost in the mists of the back pages. So why not dust them off now and then, especially for the newer members to see (in case they hadn't).