I took my first trip to Vegas in April, and am looking to go back in August. I've been getting email offers from NYNY and Luxor and am curious about the expiration dates. Specifically, the one from NYNY says "Offer Expires May 31, 2013", but then has a calendar shown below with dates through November showing which dates the offer can be used on. So, does it need to be booked by May 31, or do I need to complete my stay by May 31? Any help is appreciated.