Correct setup:logout

Hello, We're setting up our first Hikashop and trying out the new CardSave plugin - currently it keeps the (test) users logged in, even after the transaction is complete.
We're using the Hikashop login option - see
www.sightlines-initiative.org.uk/checkout -
to register the new customers, and assumed that logout was automatic at the end of the transaction, or if the user went away without completing a transaction. Should we add some login option from Joomla (1.6) and if so, how?
Thanks, Robin

Thanks very much, Robin

Could you add a button Logout for users that want to change from one user to a second user without having to wait the session life time

Thank you