Seth Yoder

When you password-protect a post in WordPress, a cookie is set to expire in 10 
days which prevents the user from having to enter the password during that 
10-day period. This plugin allows you to easily change the lifetime of that 
cookie.

Password Protection Expiration

Allows you to easily change the lifetime of the WordPress cookie which allows automatic login to password-protected posts.

TIEro

This plugin is now part of the free plugin <a href="https://wordpress.org/plugins/tietools-automatic-maintenance-kit/" title="TIEtools" rel="ugc">TIEtools</a>, which also includes duplicate post control and server log file removal.
Simple post expiration plugin. Expires posts based on a variety of criteria, including category and post status options.
<ul>
<li>Expires published, draft, pending and private posts on demand.</li>
<li>Includes or excludes user-defined list of categories.</li>
<li>Moves all expired posts to the Trash.</li>
<li>Notifies post author, site admin and others of post expiry on demand.</li>
<li>Permanent post deletion is handled by WP’s built-in Trash removal.</li>
<li>Completely automated by wp-cron once options are set.</li>
</ul>
Currently, the plugin offers four cumulative expiration methods:
<ol>
<li>Expire posts based on their age (e.g. expire posts created more than 90 days ago).</li>
<li>Retain a given number of posts and expire all others (e.g. keep the latest 1,500 posts).</li>
<li>Detect the BAW Post Views Count plugin and expire posts based on a combination of post age and number of views (e.g. expire all posts over 45 days old which have fewer than 100 views).</li>
<li>Detect the WTI Like Post plugin and expire posts based on a combination of post age and total number of likes (e.g. expire all posts over 90 days old which have fewer than 10 likes).</li>
</ol>
Each expiration check is run separately and in the order listed above, so you can build quite complex expiration structures to catch a variety of criteria.
Post status choices apply to all expiration methods. The user-defined category filters can be switched on or off for each method.

TIEexpire Automated Post Expiry

Expires posts based on multiple criteria, with category and post status options. Sends notifications to users and admin on demand.

Password Protection Expiration vs TIEexpire Automated Post Expiry