Okay, there does seem to be some time limit. To find an old thread I picked a random word likely to be used in a discussion and searched for threads before a specific date (just plugged in this date in 2005). I picked “Morons who won’t see good films” (a 2005 pit thread) and was able to reuse that title. Does anybody know the time limit? Finding it by trial and error would be tedious and annoying for everyone.