Add more than 1 password to your protected pages, also administrators and page's authors can view the protected pages without password.
You can now add passwords as many as you need on every protected page.
Why? Because you can protect page and give your client a personnal password, not just a random pasword or everyone.
Option: If you are logged as admin or the page's author, you won't need to enter password.
Option: If you set a list of child pages, just change any password (parent page or any child) and all the password for the hierarchy will be updated!