After a year of travelling around Oz we ended up with my licence and a caravan rego's to SA, car to NSW and wife got a QLD licence.
Worst is to buy a vehicle in a state where you don't live but want to stay for a month.
We traded vehicle in NSW, you have 7 or 14 days to change the rego over. Went to the rego place, got told to drive to SA change it then drive back. Got told by another person to drive it in NSW until we decided to leave, I did point out that then I would be driving unregistered but got a blank look. Ended up changing our banking address online, printing a statement showing a fake NSW address to prove residence, then changing the address back.
Bring on a national licence/rego!