We would go back very shortly if we would get snowshoes in Sydney. Three (other than two) days may be the right opinion.
Walking "easy" track of 30 KM with 1000 meters ascent for 5-6 hours many be a must before heading to Snow Mountains, to walk on SNOW for 18 KM with 650-700 meters ascent for less than 8 hours, with the aid of essential gears.