It depends on how you drive, where you drive, how often you drive etc.
Routine maintenance is preventative by nature. First, be sure to choose the right oil for your vehicle. This is vital for proper operation in the desert (or anywhere, really). While most manufacturers say that a car’s oil should be changed every 10,000 km, this is not necessarily true with every type of oil, or in every climate.
Manuals can’t be written for all cases. It is just a guideline. In our case we drive in very hot weather and push our cars so engine is running very hot for long times. Extreme heat will degrade the oil quicker. The higher the oil viscosity, the better it lubricates your engine.
Given an extreme climate like the desert, more dust gets ingested into the intake, and deposited into the oil. Dirt breaks down oil’s viscosity and this will eventually erode the seals and piston rings if unaddressed.
In the desert, you need to change your oil more frequently than the manufacturer suggests. You also need to change your oil filter a bit more frequently in the desert.