You'll prolly have to pay prorated retainer rates when your retainer privs expire. That is, you'll still have game time but not retainer time. You'll try to access your retainer at a bell, and it'll tell you that retainer's contract's expired. At that point, you go to the mog station and pay for your retainers to cover them just for the remaining game time. At your next auto-renewal (if you auto-renew), you'll renew both for game time and retainer time.
(This is how it works when you add game time cards to your account)
