.

 

never is the interval most people use. it'd be easy to flush out and change brake fluid with a pheniox injector kit. i use synthetic brake fluid, not to be confused with silicone brake fluid.

 

Frigging computer problems.

Snap-On makes this cool tool for flushing the brake fluid. It uses a compressor and sucks the fluid out each bleeder at the same time filling the reservoir. I believe the change interval for brake fluid is every 3 years.

I'm not sure on the PS system. I generally flush it whenever I have to replace something in the system. To do that I disconnect the low pressure line, have it run into a catch can, start the engine, and fill the reservoir like mad so it doesn't run dry.