Unless you mean something completely different...
It is only once per month as far as I know.
Also see this post
Under normal circumstances, your MindManager account sign in information is stored across sessions, so you should not have to sign in when using the same browser (within reason as the sign information will expire after some period).
If you are needing to sign in every time you use the app, that is not the intended behavior. Please open a technical support ticket so that we can investigate the cause and hopefully resolve it for you: https://www.mindmanager.com/en/support/contact/