So, I don't mean to downplay the quite notable achievements of the Australian economy, but the growth has been caused by a large confluence of factors which will make future growth more difficult. More than anything else, Australia's great success I'd argue has been driven by carbon. Even if you're only at 9% of gdp for exports, the impact of the economy is much higher. Look at the absolutely huge amounts spent on capital purchases and investment to fund the huge coal and natural gas projects, those don't count as exports for gdp calculations, but they feed the export industries. As we start to see China switching away from rapid industrialization and export-oriented growth to something more sustainable, you'll see not just exports fall, but also lots of industries that rely on exports. Housing has become amazingly unaffordable, which is a headwind to growth. The rise of the Australian dollar has done a number of Australia's manufacturing industry. And with a renewed emphasis on transitioning away from carbon, Australia's large resource base won't provide the same benefits that it did in the past. In no small part that is because margins are shrinking as costs of doing business in Australia are becoming very expensive. Look at the cost blowouts on Chevron's Gorgon project, or some of the mines even.
Having said all of that,I'm not intending to downplay the amazing success that they've had. I would put very good money on the line to wager that the next 21 years won't be as good to Australian economy, however, as the current run is quite unsustainable imho.