How to Re-publish Old Posts without Disturbing Search Engines
There may be situation when you would want to republish your old posts to achieve maximum benefit from your archives. Many people make a big mistake by re-posting the same article which creates duplicate content on your site. This strategy may upset search engines.
As a solution to this problem, you may change the original date and time of your post by re-editing instead of re-posting it. This will show your post, which you posted back in time, on your homepage. So now there would be no duplicate content on your site.
This technique will help your new readers to get to know about your old and popular content. Sure, the comments on that post would show the original date and time. WordPress allows you to edit the submission date of comments as well which you can find in the comments section.