when I was riding alot of moto-x we would leave the oil mix gas in the bikes for extended periods with no problems, but when I would work on restoring a older street bike or classic car(used to be quite the gear head) we would encounter a situation we called the green death.

when fuel would sit in a carb a green film would form and all the seals would go bad including the carb jets, sometimes a rebuild took care of it sometimes they were too far gone to repair.
it all depended on how long the fuel would sit.

here in CA I would run the fuel out of my engines no matter what type,because of the alcohol content, seems like the oil would prevent the death, over pure gas, better safe than sorry,not sure if aussie gas has eny methanol in it you would think so.