Other Car Rental Programs/Partners (ie. Alamo, Enterprise, Sixt) - Alamo: does Discover coupon allow change?

I'm thinking of applying the Discover Card's Alamo coupon where a $20 rebate translates to $40, for a rental at FLL in a couple of weeks. The relevant part of the T & C is:

Valid for new reservations only; cannot be applied to existing reservations or completed rentals. One certificate per Alamo rental and void once coupon code is redeemed.

I would plan to use it, but if I should postpone the trip because of an approaching hurricane or I have the flu, would I have lost it? I'd like to consider these small but real possibilities. I would probably change the dates on the reservation rather than cancel it. The base rates are already rather high; I wonder if I risk them getting higher if I wait until a closer date and I'm surer of making the trip. I used this type of coupon previously and think I added a code for extra Southwest credit after completing a booking with the coupon code; is the code "redeemed" when the booking is made or when the rental happens?

I'm thinking of applying the Discover Card's Alamo coupon where a $20 rebate translates to $40, for a rental at FLL in a couple of weeks. The relevant part of the T & C is:



I would plan to use it, but if I should postpone the trip because of an approaching hurricane or I have the flu, would I have lost it? I'd like to consider these small but real possibilities. I would probably change the dates on the reservation rather than cancel it. The base rates are already rather high; I wonder if I risk them getting higher if I wait until a closer date and I'm surer of making the trip. I used this type of coupon previously and think I added a code for extra Southwest credit after completing a booking with the coupon code; is the code "redeemed" when the booking is made or when the rental happens?

I believe most (if not all) serialized coupons are considered used if the reservation is used and/or not cancelled. If you were to apply it on the reservation and you cancelled the rez, the coupon could still be used again. If however you never cancelled the reservation, it would "lock" in to the open (but unused) reservation and would be considered used. I dont work for the marketing dept so you may want to give customer serivce a quick call, but thats been my experience in the past.