how+do+I+find+old+posts?

By clicking the page number, if it's there?! o.0

Example.

Many years ago, when the boards were constructed for IMDb, the thinking was, the conversations should remain fresh and boards would not be used to archive information (if info coming from conversations needs to be saved to IMDb, it should be submitted to the searchable database where any user, registered for boards or not, could also view the information). So, because of that and to save resources for the database itself, message board posts "expire."

Assuming they were not deleted because of offensive content, deleted by the user making the statement, or the user making the statement deleting his/her account, the messages that far back have likely "expired" and been deleted.

If you look at the board itself and go to the last page, you can see what the current expiration rate is for inactive threads. If no longer getting replies, a thread will usually be deleted in four months or so. It can be faster for more active boards or take years for slow, inactive boards (though all boards have a "purge" at a point to clear out speculative pre-release posts and start over with more active and up-to-date content.

See this "help" area page:

http://www.imdb.com/help/show_leaf?boardswhydeleted