I recently enabled caching in a Drupal site and could notice improvement in page-loading performance. Drupal can be compute-intensive, so a cache goes a long way in making your site more responsive to visitors.

There are a few options to choose from when you enable cache. One of them is the 'Minimum cache lifetime.' This defaults to '' and I think it does so for a good reason. With this setting, any time you post a content, all cached pages that are affect by that post expire immediately, so you can the effect of the post right away.