Some of those essays are good enough that they're worth resubmitting every year or so, both for people who haven't read them yet, and to see what new points come out in the discussion.
If so, maybe auto-add a prefix, "REPOST: Article Title", for any link that's re-submitted. That way people who've seen it before can ignore clicking on it, while those who haven't seen it will now have the opportunity to read it.
EDIT: BvS already posted a link to a Reddit post with the same idea.
Likewise, new situations can cast a different light on what was once written. HNers posting relevant and timely links to old essays is a good thing.
But can we limit it to one resubmit per year? After a couple times in the same year, my patience grows thin. After all, HN has a lot of really good essayists out there, folks who can be just as helpful. As nice as PG is, we don't want to give him too much exposure. After a while anybody can start to sound repetitious, like when they go on and on about something. Sort of like repeating themselves. Over and over again. The same thing.
Gets annoying.