ofredon

Password Form Styler lets you easily style and customize the default WordPress password form used on protected posts/pages (Password Protected).
It applies globally to all protected pages and provides an admin settings page with a live preview.

Oxicat Password Form Styler

Style and customize the WordPress protected-page password form, globally, without editing your theme.

Mike Hickcox

Set the time allowed before a password must be again entered for a password-protected post or page. Also, enhance the page password form. 
By default, when you password-protect a page or post in WordPress, a user can get back into that page, without a password, for 10 days. 
With this plugin, you can set your own duration, and allow for better protection of password-protected pages. 
* This plugin allows you to easily change the lifetime of that cookie. 
* Set it to any combination of hours, minutes, and seconds. 
* You can even set it for zero hours, zero minutes, and zero seconds, so users always must use the password to access the page. 
* The page password form is also enhanced for a better look in the website, and shows the user the length of time allowed before a password will again be required. 
* If you create pages with a builder, that system may overwrite the password page created by this plugin, but the times you set will still work on your website.

MC Protected Page Upgrade

Set the time allowed before a password must be again entered for a password-protected post or page. Also enhances the page password form.

Oxicat Password Form Styler vs MC Protected Page Upgrade