I don't think we should categorically block edits to old questions; if someone comes across an old, unanswered, little-viewed question and that's because it's badly written, I want that person to improve it if possible.
However, I ask people to be mindful of the effects of editing: an edit bumps the post, which is right and proper, but bumping old posts 20 at a time pushes 20 newer posts off the front page, depriving them of attention. So, try to be polite -- edit things that are already on the front page or do older ones in smaller batches so that we can help people who had great questions just yesterday, too.
Also, in the current case many of the edits were done by people without enough reputation to edit directly. That means people needed to approve those edits. When going through the suggested-edits queue, it's a good idea to be mindful of the cumulative effect of your approvals. Maybe some suggestions should just wait in the queue a while longer. (Or if they're too minor, you can reject them.) If we all try to do our part we can improve the posts on the site without pushing new posts off the front page too quickly.