are you talking reward or paid travel. Either way I think it is 330 days out.

but if paid, I would wait for sales etc closer to date. Put your money to work for the year and pay at the end.

We just booked two tickets to EZE via SCL for less than $1200 each from Calgary (with 15% end of year bonus discount and sale fares).

Come October/November would be a good time to start pricing.

Remember also Continental (now United) flies via Houston with some good schedules if you don't want to stop in SCL (AC always stops in SCL en route to EZE)

If doing reward travel, then best to jump on it at 330 or 335 or whatever it is in advance of trip (trouble is you can't book return until it is available 14 or 21 or 28 days depending on your planned trip length after booking is available for start of your trip.)