It seems that these stones vary from one to another in terms of hardness/softness and cutting speed. So 75 might be a bit excessive for some and not too bad for others. And the fact that personal technique is a factor just adds to the variation.

But that raises a good point, try testing the edge after every 10 or 20 strokes, see if you can accomplish the same sharpness in fewer strokes. Never know till ya try (unless you already have, in which case, carry on as per usual).