Well, long flights are always easier with little to no turbulence which you won't find out until you're in the plane obviously. But my last flight was Dubai to Washington 14 hours and the first 5-7 hours was turbulence non stop! Terrible! I think Cali to Australia is about 14 hours also.

I always bring my own pillow. Maybe it looks goofy sometimes, but if I find a nice spot against the window it works out great. Also check the seat map up until day of departure, try to get the seat with no middle passenger!

You'll be fine. Don't worry