It seems from this advice that we are no longer allowed to carry duty free liquids into Australia?
"Duty-free purchases:
Customers who are flying out of Australia may carry items purchased from Australian duty free shops.
For flights departing Singapore, duty free items are allowed into Australia provided these items are purchased on board or are delivered by duty free staff to the gate-hold room in a sealed bag.
Customers who are entering Australia via transit in Singapore will NOT be allowed to carry duty free items purchased from previous sectors."