Hi,
No, the email address and billing/shipping address won't be kept if you come back at another time.
That's potentially only the case for some payment methods and only while your user session didn't expire yet.
But normally, when someone comes back on your website, his user session has already expired and thus he will have to reenter everything.
You can configure the duration of the user session in the settings of the Joomla configuration.
If you don't refresh a page of the frontent during the period of time you entered there, the user session will be cleaned and you'll see that you'll have to reenter everything.