I am trying to search for some threads in suspension/handling and they only go back to Sept, 1 2006. Now I could be wrong, and NOBODY has made any posts in that section up until a month ago, but I don't think thats the case. Do these older threads get deleted after a certain time period, or is there some form of archive they go into??

you need to change the settings in the search form.

How do I do this?

From the search page, choose a different date range for the "Search Posts From..." select box.