Many search engines have stated time and time again that they crawl pages they can get to easily. Basically, if it takes more than three steps to get to a page, it won’t get indexed as easily or or re-indexed as often. By adding related posts to your blog, you are now allowing a search engine spider to easily get older posts easily.
Related posts are just links to posts that were made in the past. Some may have been posted in the last week, others maybe last year. These posts have a much better change of getting updated in search engines then if they were buried in the archives.
Creating links to related posts can be done in a number of ways. One is just linking back to old posts within new posts as reference points. Another is taking the time to write out three our four related posts at the bottom of all new posts. This may be a bit more time consuming, however they will be most relevant.
What I chose to do was install a related posts plugin. Or as I like to call it, possibly related posts. It automatically looks for related posts based on what it feels is important (on active/passive keyword matches to be technical). The posts may be related, but then again, they may not be. From what I’ve seen, it does a pretty good job.
Adding links to related posts in your newer posts will help search engine spiders crawl deeper into the site easier and get more pages indexed. Sure, search engines will eventually get all your pages, but related posts will make it easier and more efficient.