I think we should encourage the user to update the old post. Some old post may get hidden because of low reputation or bad timing and some articles deserve to get more attention. It is unfortunately that they get hidden due to various reason and it will be great that if people be selective and repost some of the great stuf
Yes. The best posts should be the ones features, regardless of age. Other sites such as Quora show great answers sometimes dating back to 2011.
However, I'm not sure if the edit block is due to technical limitations.