I was just reading this on the Azamara site:
Complimentary Nights may only be redeemed on voyages of seven nights or more and must be redeemed at the full fare rate and cannot be combined with other promotions, except the Onboard Booking Program, Early Booking Offer, and the FCC from the Refer & Receive Program.
So it looks like you could use them on the Early Booking Offer which might make it a better deal.