NO Rewards Available for Six months
MARYG, I was stunned to say the least when you said that you couldn't get a velocity reward point flight MEL - SYD in the next six months!
I did some checking up, there are in fact seats available every day, checked with Velocity as well. Even if it is the very last seat available on that day it can be redeemed using points, as long as you have sufficient points available. i would suggest there was some error at the time you checked. I was panicking that my points were suddenly worthless.
Hope you find your flight !