Maybe you already know(I could be using the wrong words).
After you get about 10-15 pages of posts on your thread, it will 'Lock' - meaning no one can add any comments to it. You will see only a little 'Notify' box in the bottom right of each comment instead of the typical 'Reply', 'Edit', etc.
In order to continue on, you have to begin a new thread. Many will put a link to their old thread(s) in their signature to make them easier to find.
Hope that helps. If I have left anything out, someone please feel free to add or correct this.
