most cars are a fill for life fluid. but as a bitoger, you know that its youre duty to change it ATLEAST once every 100K miles. think of some boy scounts responsibility motto playing on a boom box in the background as you read my text. forget about fill for life. that does not mean for the life of the car, that means for the life of youre power steering components which will be reduced since it never gets changed by most people. (sarcasm).
personally i do it every time i change the brake fluid, which is every time i change the transmission fluid, which is every time i change the diff fluid. every 2 years on the first available weekend in march, usually in the evening time, perferably with a few bacardi o3's in a styrofoam cooler.
powersteering systems do not hold much fluid, typically a single quart or at most 2 quarts, so from a cost perspective, theres no reason NOT to change it out once in a while. the job is rediculously easy on most cars. just remove the rubber return hose from the resivour, plumb it into a oil change bucket, and jack the car up and turn the steering wheel left and right over and over with the engine off. besides a basic pair of plyers to get the hose clamp off the return line, you dont even need any tools. the rack will "pump" fluid out on each left and right turn you make on the steering wheel, which flushes the entire system of old fluid without mixing it in any significant quantity in the new fluid. just keep flushing untill the old fluid turns into new fluid, at which time you reconnect the return hose, start the car and turn the steering to work out any bubbles. do a top off and go for a 10 minute drive. come back and top it off once more and you are good to go for another few years.
its the duty of every bitoger to change that fluid out atleast once in a while. minimum 100K miles is what i say. thats only the minimum. boycott lifetime fluids!