I'ts my expectation from reading the source and documentation that upon authentication, any new web-request made with a valid authentication will re-new the lifetime of the authentication cookie.
So if you have a 10-minute cookie lifetime, making at least one request before the 10 minutes runs out will reset the counter to 10 minutes again.
Looking at the source (and my cookie-tracker), I;m not seeing the expire-time being reset when new cookies are sent.