https://myaccount.google.com/signinoptions/two-step-verification https://myaccount.google.com/apppasswords https://developers.google.com/identity/protocols/oauth2
Support in Google and Firefox. Google has 10MB limit before storage permissions average processing power of average computers
A million seconds is a bit less than 2 weeks. A billion seconds is a bit more than 30 years. A trillion seconds is a bit more than 30,000 years.