I am by no means a tax expert, but for whats its worth, i believe that he old 183 day thing is dead.
If your family is in Oz, and you can be shown to be effectively an Oz resident for tax purposes (which i believe you would for 183 days), your tax would be higher because you don't qualify for the tax free threshold.
I am lead to believe that about 106 days is the limit.
There has been much discussion here about this, and others can probably help you more.
Beware the Aussie tax man. They take no prisoners.