how can i hide posts after 30 days away from search?
 

How can i set a general setting.. to make threads 30 days and older not searchable by the search function on the forums?

is this possible?

No there is no setting for this. What is the reason you want this?

I'm running a trade forum, and the search function is going to be used.

I dont want people finding dead posts that are MONTHS old.

hence why.

Doesn't the database-based search time out after 10 days or so?

You just have to force the search to only search a month or newer - the "optional" functionality already exists. Just have a look on the "Advanced Search" page.