Automatically delete pending posts older than X days?

I'm building a site that is using autoblog to generate posts from various feeds. I have set it so that all of the posts will be created as pending, so my client can choose which ones he want to end up on the site.
This is going to create a ton of pending posts that will never get used. Is there a way to make it so that pending posts older then a certain number of days it will automatically be deleted?

I figure it would be a function that worked something like this:
If: post is > X days old
When: post status= pending
Then: move post to trash