If you have been running a blog for any period of time you will know that content tends to die off in terms of search engine referrals, there is usually the initial boost when you publish the content where it is fresh and gathers the most social media shares and if you are lucky it obtains a good ranking in Google. As time passes, usually over a year, that piece of content will start to move down the rankings as it becomes replaced with more recently published content. You could choose to publish a new piece of content on a similar subject, thinking that its better to have two ( or more ) pieces of content on your site which will increase your chances of being found for that subject.
Unfortunately that is not really how it works nowadays – Google would much prefer you to have one really good piece of content on the subject and direct traffic there, rather than having several which are lower quality or outdated, this is part of the Panda update which happened which punished sites with lots of “thin” content and rewarded sites with better stand-out pieces of content…
How To: Update Old Posts Correctly to Help Your Visitors & Boost Your SEO
