How often your Australian Shepherd requires bathing depends on where you live, how much time he spends outside, and how dirty he gets. Like kids, some Aussies have a knack for getting dirtier than others. A working dog may require bathing on a regular basis, say, every 4 to 6 weeks or so. Aussies who spend a great deal of time indoors may require bathing once every 3 or 4 months. No cut-and-dried formula is applied.