1998 Ford Contour Need a second opinion - Flushing Brake, P

The Ford is running great right now after having both its engine and transmissions completely rebuilt about 4 years ago. For the last two years, the car has been driven about 750 miles per year. We took it in for a routine oil change and tire rotation (Understand oil change should happen about once per year regardless of how little the car is driven.) The dealer we take it to recommended that the Brake, Power and Transmission fluids all be flushed now. From past maintenance records, it does not look like these fluids have ever been flushed before. How often should these fluids be flushed?

Thanks!