How can we keep track of my years of membership when every password change creates a new membership and drops the previous years?

As long as you use the same username, you aren't creating a new account, you are just changing the password. 

 

If you have multiple usernames, but use the same email address, you can get a list of all of your past usernames.

 

If you click "Forgot Username or Password?" you will get an option to use your phone number, email or user ID to retrieve your account. You should see that option in blue underneath the login button. 

 

If you provide an email address, you will get an email with every username you had associated with that email address.