Originally Posted by Dave Noble

They should just check luggage to Perth

If you are on 2 different bookings and misconnect , then you are down to whether Qantas chooses to assist. Being 2 bookings, the airline is under no obligation to assist and just hold you to fare rules of purchased ticket

They alternatively may just rebook you for no charge

Personally, whenever on separate bookings I always leave a decent margin in case problems occur