Mine will sign me out maybe once every 6-8 weeks. Most tech companies do this as a security measure, because allowing indefinite periods of being logged into a service leaves you, and them open to abuse, fraud, attacks, etc…
I use a password manager (LastPass), so no need to remember all your passwords. Strongly recommend if this frustrates you, or you forget your passwords.
If you’re not receiving the password reset email, it might be in your spam folder. Failing that, just send them a support ticket, my experience with that has been good, they respond within a day or two usually.