Hey I recently updated Extended Comment Options. This lets you close posts on more than one comment. Great if you have a lot of spam and you want to close comments on old posts.
New features include an automatic feature -- set it and leave it running. You can leave comments open on the last 5 posts, say, and close the rest -- plus loads more. Or you can close comments once they go beyond a certain number.
If you've used it before, check it out, it's a lot simpler to use now!