Originally Posted by
jeffypop75
From my experience when you cancel booking and get a credit, the discount code remains attached. When you call to rebook using the same PNR, the discount code applies to the newly selected flights. I've had this happen a few times with % off codes and comfort for the price of flex codes. The agent told me they could see the discount code already applied. I suspect you still need to stay within the expiration window of the code but I've never had to rebook past that so I can't say for sure.
When you retain the credit to rebook later, you also retain the PNR and its creation date, which is why the promo code would still be attached and the discount still applies. You would only need to ensure you are not booking outside the travel period or inside the blackout period stipulated by the said discount code.