25 you can link the new one and the old one and they will stay on the boards for quite a few years.
I don't know how they decide what to delete but there are many posts still in the archives.
To link threads. Copy URL from 1st page of old thread and paste it on new thread. Then copy URL from new thread and paste it on last page of old thread. When you are done, hit the notify button and ask moderator(Virginia) to lock thread for length.
