If you're looking for posts on a certain topic, use the find button, located on the top of every page of the discussion board. This not only helps take you directly where you need to go, but also keeps repetition of posts to a minimum.

The advanced search on the board pages searches for words only in the discussion board. Hence, by using a keyword, you can easily look up the topic you are searching for, or even bring up a favourite post from an old thread.