I leave comments open on my blog, mostly out of inertia. It's mighty rare that I get a comment on something that's more than a week or so old.

My own opinion is that that comment forms should include a preview box (there's a WP plug-in for this). I tend to reply to most comments, but I don't want to be the only voice. I probably account for nearly half the comments (it's those replies to comments from others).

I do wish WP wouldn't include as pings my references to my own stuff; I suspect 80% of the alleged pings take that form. So it goes.

Harold, re Virginia's moderation, in WP 2.7 / Settings / Discussion, I see you you can automatically close comments after X days, but I don't see anything to set them to moderation after a time.