Proactive ghost busting?

Ever considered having topics automagically close themselves after some unreasonable amount of time with no activity. Every so often it seems that someone discovers the site, reads through a bunch of it, and starts bringing a bunch of threads back from the dead. I'd think that if a topic has gone without responses for more than, say, 90 or 180 days, it really ought to just die. If someone wants to talk about that topic again, start a fresh thread; reference the old one if it is important. Maybe exempt pinned topics, but you get the idea...

--Dave Althoff, Jr.

I suppose there could be an automated way to do this, but would it be worth the effort given the infrequency with which it happens? We've got enough moderators around I think to be pretty proactive about it.