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.

abmcr

Enable Posts and Pages to automatically expire and change at a certain time, and provide notification of expiration.
<h4>Notification Options</h4>
Simple Expires also notify you:
<ul>
<li>When expiration occurs</li>
</ul>
This reminder helps you keep content fresh, providing a reminder that content is out of date and needs updated or replaced.

Simple Expires

Enable Posts and Pages to automatically expire and change at a certain time, and provide notification of expiration.

Password Protection Expiration vs Simple Expires