@mrvietnam thanks. Appreciate the advice!
FYI regarding expiration from the Terms and Conditions:
The promotion period
The promotion period is from 1:00 ET June 16, 2022 to 23:59 ET on July 13, 2022.
Click “Activate your Stampcard” button to participate in the promotion. You can collect the Stamps in any order of your choosing. On collecting all Stamps within the promotion period, you will be eligible to receive a $10 credit.
The $10 credit expires 365 days after it was received.