The AA web site states:
Admirals Club Members must be departing on an American Airlines flight. Eligible AA customers will need to present an invitation letter, that can be obtained at the AA Ticket Counter or Transfer Desk, to the Terraces Lounge for admittance.

Has anyone had to present one of these "invitations" yet? If so, what do you do if you want to leave the Terraces Lounge (or F/C lounge) for a bit and come back in?? Will one "invitation" get me into both lounges (if I'm flting in F) or do they take the invitation when you enter one of the lounges?