Split Reservations
While not directly applicable to this situation, especially since a 50% off award was used, I sometimes make split reservation with my 5 night for the *point cost of 4 booking immediately preceded or followed by any additional nights I may want. Then if there is a need to shorten a stay I have some additional flexibility. Just did this for a St. Maarten trip next January - especially since I'm not sure what flights will be available. Book now and cancel as necessary.