my brother is in Brazil, his all 3 phone blocked exactly after 6 months and an additional grace period of 40 days..
now need to register with local telecom authority, caz after 6 months u r not really a visitor category person..
so, if u r staying in australia for longer period of time, something similar can happen with u, so take the right advice and get a fone from there, u can bring ur current device with u, it wont harm anyone..