Off T:
That certain TV show, now cancelled, does give a clue why ABF take a keen interest, on too many regular runs.
Yes, as Aus citizens, they cant stop you, from entering, but they can make it hard, esp if you have got dom connections, as they can be very persistent.
Too, they also have CTF and AML and also the other thing rules (some people also bring in cd/dvds of non allowable items), they have to check on, some muppets bring in and out more than Aud$10k and do not report it, this makes it harder for bona fide SC run chasers.
Not to mention cigs.
Its worst, if they decide to do the wand, this one for drugs.
They will ask you to go as far as to open your bags, they then/then they will decide to swab items, of yours.
And even if negative, they can still ask questions.
Probably it would be a good idea to show, that you are working, or have a means to support yourself, and are not on Centrelink.On T.