Picking a time or milage for the power steering flush is totally up to the owner, 4-5 years or in the 50-70K range for mileage sounds good.

The power steering pump has two lines attached to it. The line that screws in is the discharge line (larger of the two) and the line that has a hose clamp (smaller of the two) is the return line. Raise the front wheels off the ground, disconnect the return line and catch the fluid that will run out. Put a cap/plug on the return line nipple on the box. Fit some clear hose over the return line hose you disconnected and route it something to catch the fluid. Top up the fluid, then inside the car turn the wheel right to left, this will force the fluid through the system and out the return line, keep your eye on the fluid level, topping up as you go. I use 3 quarts, and any fluid that meets or exceeds Type "F" would be OK, Synthetic AMSOIL certianly exceeds the specs. Don't start the engine, do the wheel turning with the engine not running, or you will be out of fluid faster than you can fill it and the entire rack will not get flushed.