do they have to be used or booked by 12/31?
IHG Twitter sent me this:
Unfortunately, the free nights expiring Dec 31, 2021, cannot be used to book for future stays in 2022. We encourage you to redeem and use them before the expiry date. However, we have extended the expiry date for the free nights earned for the year 2021, through December 31, 2022. Thank you.