Gosh that is a though spot you are in - flying twice per month between antipodes (cities that are almost 11k miles apart). There are very few of those city pairs in the world. Its 2 x 12h flights every 2 weeks and 12hrs+ jetlag - sounds like perfect FT torture to me

However to give you relevant advice - give us some more details. Do buy your own tickets? If not what airlines will you be most likely on and what class?

Emirates is really popular in Perth and they plan an ORD flight in 2012. Plus they have great planes. But their Frequent Flyer program is somewhat limited.

Qantas is the obvious other choice but you need to connect twice (LAX /SYD) and awards are really expensive with them.

If you can fly business United (but please never fly Economy there) is a good choice I guess with two connections as well. You will be Premier 1k in no-time. Awards are really fairly priced.