1. It’s possible to pre-order duty free stuff for collection on arrival back in Melbourne.
“If the goods are to be brought back into Australia, please be aware that they may be subject to GST. Normal passenger concessions apply and include any items for which a TRS claim has been approved (excluding most personal items such as new clothing, footwear and articles for personal hygiene and grooming). If the value of those goods together with overseas purchases exceeds the passenger concession, the goods must be declared to Customs on your return to Australia. Penalties apply to undeclared taxable goods.”
If in doubt you should declare the goods to Customs on your return.
This is the really important bit…
3. For stuff that you already own and are not claiming TRS on, you need to fill in a form (we will need to do this with our iphones and cameras and widgets and wodgets)
This is the critical form to ensure that you don’t get stung with duty and GST for stuff you’ve already paid for. It means these items are not counted in your duty free allowance either.