Love it! I have tried all the major password managers for Firefox, and Keeper is the most consistent and reliable. I am a retired programmer and fairly obsessed with finding the best security and password apps.

When I first setup the addon, I was having some difficulty with 2-Factor Authentication, where Keeper was requesting the 2-Factor code on every signon. Then I realized that you need to retain the cookie info for Keeper - I was clearing all cookies on exit from Firefox. So, I made the following changes in the Options and Privacy & Security section of Firefox:

For "Clear history when Firefox closes", set Cookies to "unchecked".
Under the cookie options, set "Keep until" to "I close Firefox".
Under the cookie "Exceptions", add the link "https://keepersecurity.com" as "Allow".

After the above changes, Keeper will only ask for the 2FA code on the first logon, and the Firefox cookies will still be cleared on exit from Firefox (except for the required Keeper cookies).

Hope the above helps someone, as it was driving me crazy.