The best use is a flight that you have enough points for when you want to go.
You do know the seasons are opposite down there?, so research your destination to find the best time to visit. I prefer shoulder seasons when there are less people and lower prices.
Booking availability starts 331 days with most airlines and AUS/NZ is one of the most popular awards so search as early as you can on whatever airline you go with.
You can get more bang for the buck by waiting for a bonus promotion to trade your amex points for airmiles, they often run promotions to get an extra 20-50% on airlines such as BA, AA, DL.... wait for the best one of those you can get, transfer your amexand add points to that program until you have enough for your award tickets, get a credit card or two to help the points add up....don't worry if it's not AA you can use their points for hotel and rental car instead (at least in Hawaii, I don't know about down under.)
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