Will the power steering system last the life of the car without maintenance?... perhaps. Wear particles develop in the system that can accelerate wear. Changing the fluid flushes away the debris, and hopefully prevent problems that can develop later. I don't recommend it for someone who needs to pay a mechanic to do it, but it's a good maintenance procedure for the DIYer.

Flush Power Steering Fluid

1. Lift front tires off the ground.
2. Disconnect the ps return line, drain ps reservoir.
3. Plug open connection at the reservoir.
4. Secure the return line to a generously-sized container (at least one gallon). If needed, add a length of hose.
5. Fill reservoir.
6. Line up your bottles of new fluid for quick pouring.
Here comes the fun part...
7. Have helper turn car on, and immediately have him go through full range of steering motion (left and right) and shut off car, all the while you are trying to keep the reservoir filled.
8. Button everything back up.
9. Clean up mess.
10. Top off fluid.

The front tires must be off the ground so the system is unloaded, otherwise the fluid comes out with a lot of force. The return line must be secured to prevent a big mess. Keep at least a gallon of ps fluid on hand. The helper must know what they are doing.

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95 E320 Cabriolet, 169K