Members may determine if a hotel has Free Nights available by visiting
www.priorityclub.com/bookfreenights and searching by city or date. Rooms are limited, subject to prior sale and may be unavailable during high demand periods. Each participating hotel has limited room inventory available for Free Nights.
And another warning:
1.) Will the redemption participation list be different from the earning participation list? \
2.) The "limited" rooms inventory for free nights is also a bit of a red flag. Atleast with SPG this is never an issue as long as any standard room is available.