TIEro

This plugin is now available as part of <a href="https://wordpress.org/plugins/tietools-automatic-maintenance-kit/" title="TIEtools" rel="ugc">TIEtools</a>, which also includes post expiry and server log file removal.
A simple duplicate post deletion plugin. Spots posts with the same title and removes all but one of each.
<ul>
<li>Checks in published, draft, pending and private posts on demand</li>
<li>Includes or excludes user-defined list of categories</li>
<li>Moves all duplicate posts to the Trash (leaving the oldest or newest original copy)</li>
<li>Permanent post deletion is handled by WP’s built-in Trash removal</li>
<li>Power button to switch everything on and off without messing with the plugins page</li>
</ul>

TIEdupedeleter Simple Duplicate Post Deleter

Simple duplicate post deleter. Trashes duplicate posts based on status and category. Keeps newest or oldest original copy.

Electric Studio

javorszky

Adds an expiry date and time to posts, pages, or custom post types in which the post becomes a draft.
<ul>
<li>Supports custom post types</li>
<li>Allows admin to choose which post types can expire</li>
<li>Sets expired posts to drafts rather than deleting them</li>
<li>To show an expiry date on the frontend, use shortcode [expirydate] else function es_ape_exp_date()</li>
</ul>

Electric Studio Auto Post Expire

Adds an expiry date and time to posts, pages, or custom post types after which the post becomes expired.

TIEdupedeleter Simple Duplicate Post Deleter vs Electric Studio Auto Post Expire