This appears to be a new offering from Reward Gateway as I have not noticed Airbnb in their offers before.
It has been added to the eGift wiki, I have checked a number of the other rewards programs but so far this is the only one I have found with Airbnb gift cards.
Once you redeem the gift card (https://www.airbnb.com.au/gift), the balance remains on your account indefinitely until you spend it.
How do I access Reward Gateway?
Your employer needs to be subscribed to this program before you can apply to access the program. Once you are given access, you can log into Reward Gateway through:
The dedicated website for your company, or
The SmartSpending app on iOS/Android devices.
… and more details on Reward Gateway here
Airbnb cards are on promotion at Woolworths from Wednesday morning with 20x rewards points.