Forgot to reply back to this thread, but thank you for the insights! In the end, my mother called Hyatt and they did extend the validity of her free nights for +1 month -- perfect! As for our visit in Japan, we very much enjoyed a mix of free night awards and revenue stays at PH Tokyo, GH Tokyo, HR Osaka and HR Kyoto -- the experience was actually enough to make me decide to go with Hyatt now over SPG (also glad to have completed a Diamond challenge just before the visit that was well worth it)!