The ATO rules on losing your Australian tax residency have become much stricter in recent years so it is difficult to lose Australian tax residency unless you basically burn all your bridges and connections in Australia.
I ceased to be an Australian tax resident more than 30 years ago. At that time it was relatively easy to lose Australian tax residence and I don't think the ATO particularly cared at that time. Also, I was young then, had no "home" in Australia, visits to Australia were infrequent, no Australian wife or children etc.
As I have been outside the system for so long I am able to retain my non residency but if the current rules applied to me leaving Australia today, I doubt I would qualify as a non resident.
After more than 30 years, I intend to return to Australia within the next year and become a tax resident as, believe it or not, Australia is a relatively low tax jurisdiction for retirees (might change after 18 May 2019 and so may my plans).