I always knew you could change date but the fact you could change destination and class was a surprise, i.e. you can book a reward just about anywhere and don't have to think about getting even the destination correct. That's very flexible IMO.I did something similar, I had points in an Etihad a/c expiring in Dec 2015, bought a reward ticket for March 2016 the date of which I will change when I know the exact date I need to fly