Prune posts hack???

I did a search for this and could not find it.

I am looking for a way to delete posts that do not have responses after a month or so. The only options I see are by user and by date. I do not want to prune all messages on a certain date.

The reason I am looking into this...I wanted to have a forum where the news posts I make on the site can be discussed on the forums (and I link to the forum discussion on the news post). I know that each post will not necessarily have a discussion and did not want to have a slew of posts with no responses.

Is there a hack in place for this already?

Thanks.

Micky