While this could be a good idea (just to be consistent), I don't think this was really meant to be a badge to "Go get it". This badge is more meant to be an encouragement to think about editing when you are browsing old posts. At least, that is how I made progress towards this badge: I read a lot of old posts, and if I see something I can improve, then I do so.
It is generally not a good idea to randomly start editing old posts, since this floods the "last active" page. While one or two edits are not a problem, more than that push fresh questions off the list, which is a problem, especially on small (beta) sites.