Cashback from a purchase refund will be valid for 3 months, whereas cashback obtained from promotions are subject to the terms of the respective campaign.
Once the cashback has expired, it may no longer be used to make a transaction nor can it be converted to cash.
*Note that this cashback will automatically be utilized to offset your next purchase with Fave.
*Cashback from promo code usage is valid for 30 days from the date of issuance, unless stated otherwise.
You can look for the validity of the cashback instated on your end from the App> 'Me' tab > My Cashback as per the screenshot below: