Looks like Adelaide to Wagga Wagga is about the same length as Sydney to Mildura:
https://maps.google.com.au/maps?saddr=Mawson+Lakes+Hotel+%26+Function+Centre,+Main+St,+Mawson+Lakes,+SA&daddr=Mildura+VIC+to:Hay+NSW+to:Wagga+Wagga+NSW&hl=en&ll=-34.452218,143.272705&spn=7.326727,9.799805&sll=-34.651285,142.987061&sspn=7.309269,9.799805&geocode=FXvY7P0dECFDCCGrDUa_SP1YuCk3i7N887awajGrDUa_SP1YuA%3BFaMN9v0dGNJ4CCnDmffsaQTDajHw1KAwpHkFBQ%3BFf9t8f0dLiOiCCkR7xklyX7gajHgJESQtAkGBQ%3BFZkI6P0dkWDICClvn-CIR5kYazFQ70OQtAkGBA&oq=hay+&t=h&mra=ls&z=7
Also appears to be decent size towns for fuel stops every 300km.