Adelaide to Melbourne, there are also small towns worth visiting on the way. I see others saying to reserve five days in the guidebook ?

Australian small towns are mostly alike. They are almost deserted during the day and pitch black at night. Some travel guides have good writing skills, but they also mislead others in self-indulgence. In Australia, cities with several tens of thousands of people are considered large cities, towns with several thousand people are considered towns, and towns with several hundred people are considered towns. Villages with tens of people are marked on maps, and blank areas are definitely uninhabited areas.

In my opinion, 3 days are enough.