I will leave it to others way more expert than me on the best ways to maximize the value of your points. But I would like to echo the point already made about it being high season. Not only are both New Zealand and Australia attractive to tourists at that time due to them going into summer, but huge numbers of expatriate New Zealanders and Australians return home from all around the world for Christmas with their families (a bit like how many Americans travel at Thanksgiving). So cash fares are always higher than normal around Christmas and airlines are not so likely to make large numbers of seats available for award bookings if they can sell them for cash.