[142 Guy]

Setting aside friction in the steering mechanism, stress on the steering box is caused by the friction at the tire contact patch, specifically the resistance to rotation around the vertical axis at the contact patch. When the car is not moving or moving slowly the faster you rotate the input shaft to the steering box the greater the torque applied to the input shaft with the potential for higher wear. A column mount EPS does not alter the source of the stress or the maximum stress on the box. If you have big arms and a hoola hoop sized steering wheel you can generate just as much input torque to the steering box as a wimp with a 14" steering wheel and column EPS.

If the EPS facilitates endlessly rotating the steering wheel back and forth quickly while you are sitting in the parking lot, perhaps it will contribute to wear in the steering box. If the EPS facilitates driving the car with a persistent tendonitis resulting from too many botched slice serves on the tennis court I don't think accelerated wear is going to be a material issue. As noted, if you are concerned about steering box wear avoidance of the 205/60R15 tires would be the hot ticket.

Recognizing the inevitable ageing of the original steering box, perhaps my next project is looking for a front steering rack for the 140 that addresses the box wear and friction problems and does not create new steering problems.