I haven't gotten mine yet, but they are supposed to expire one year from the date of issue. I suspect they basically use IVANI award inventory (like they did with the other Free Night promos).
1 Free Night Certificate:
Please allow 6 to 8 weeks from your account anniversary date each year for the Anniversary Free Night e-certificate to be emailed to you. ("Anniversary" is the date that is twelve months after your enrollment date, and the same date each twelve months thereafter.) Annual fee applies after the first year. For pricing details, please see Pricing & Terms. Chase may close your credit card account or suspend your right to use your credit card account, at any time for any reason, including account inactivity. A valid email address is required in order to receive your Anniversary Free Night e-certificate. The e-certificate will be emailed to the address that is on the Priority Club Member Profile at that time. You must maintain a current, valid email address in your Member Profile and opt in to receive Priority Club e-communications in order to receive the Anniversary Free Night e-certificate. Anniversary Free Night e-certificate is valid at hotels in the Priority Club Rewards Family of Brands and must be redeemed within 12 months from date of issue. Free Night e-certificate reservations may not be made at All Inclusive hotels. Free Night e-certificates are valid for one standard room night rate and applicable taxes only. Rooms are limited, subject to prior sale and availability of allocated resources and may be unavailable during high demand periods. All reservations that will utilize the Anniversary Free Night e-certificate must be booked by calling the Priority Club Service Center at 888-211-9874. You must present the e-certificate at check in either in printed format or on your mobile device. E-Certificates may not be transferred, extended beyond the expiration date, redeemed for cash, or re-credited for points. Individual hotels cancellation policy applies to the use of the e-certificate. Cancellation fees apply if cancellation is made outside of the hotel's cancellation time period. Anniversary Free Night e-certificate rules and regulations are subject to change. Chase is not responsible for offer fulfillment.