For a long time now, WordPress has had a setting that enables you to automatically close the comments on older posts. I’ve never used it on this blog, because it makes a blog a little less open and interactive. Those are things I care about, but I find myself forced to reconsider.
Even with Akismet enabled, spam on this blog is getting out of hand. I;ve had to manually moderate almost 1500 spam in 2011, and half that so far this year. From experiments over at my movie review blog, I found that using this setting greatly reduces the amount of comment spam. Older posts will generally have acquired more PageRank, making them more attractive to spammers.
I’m going to go with 365 days for now, but I’ll be playing with that value over the coming months to see where the sweet spot is. I hope you’ll understand.