I've done the Sydney - Adelaide - Sydney run may times, a few in a Mini, I wouldn't do it these days, but in the 80's I came back from Adelaide in under 14 hrs - including breaks - in one of my GTs
Excuse my ignorance, I never realised how big Australia REALLY is - intrigued by your above statement I checked on Google maps - and got carried away by making a virtual roundtrip, which apparently takes a bloomin 135 hours of continous driving