I have been using the site a bit more recently and have been looking at deals that once clicked through have expired.
Here's the problem that I see, I can't expire threads on my own, it requires someone else to come alone too? Problem is that these threads have a much lower traffic than something on the homepage.
I suggest that maybe the longer a thread has been "inactive" the easier it is to expire, so a thread that has been inactive for a month can be expired with one click. This would help clear up the vast number of older deals which have actually expired but nobody has marked them.