DRY is a bit of a mantra with developers. It means Don't Repeat Yourself.
It should be a mantra for content owners & creators too. From a developer point of view it makes code much more manageable and maintainable. The same applies to building your site and most CMSs offer some sort of 'Token' system so that you can create blocks of regularly used content and then drop them in wherever you need them. Drupal offers a number of ways to create content once and then use it wherever you need it.