I think what this idea is calling out is that whatever you sent in the email a year ago is probably stale now - it answers the question for that time, but not n

I think what this idea is calling out is that whatever you sent in the email a year ago is probably stale now - it answers the question for that time, but not necessarily for right now, whereas a wiki should have versioning. Unfortunately once you update the wiki, it also grows stale after that moment, so in someways intractable :)