As you know, I've been been pretty fed up with the comment spammers. I have now chosen not to be a pawn in their silly game any longer.
I have now closed the comments on all but the most recent posts on this site. As it is now, any post that is over 15 days old has the comments "closed". So far, I haven't seen comment spam at all since closing these comments.
I'm betting that the lecherous spam-bots focus on archived posts more than current ones. Perhaps their system looks for posts that are over 30 days old. I'm hoping to find the sweet-spot where I can keep posts open for a maximum amount of time without attracting spam.
To close the archived comments, I used MT-Close2 (by The Dead One). This will allow you to easily close all the comments or trackbacks on any entry that is "X" days old.
Also, I use Jay Allen's MT-Blacklist for blacklisting and most importantly for despamming (removing the offending comments).
It's so nice to have these tools available- they have made my life easier.