Crusty,
I personally have gone more to using a food processor, but your experience using a stand mixer seems similar to mine except that I use a Kitchen-Aid stand mixer rather than a Viking, which may not be exactly comparable.
The more important question is the one you ask about the effects of mixing time on a dough using high-gluten flour. The important thing to keep in mind is that it is not only the time that a dough is kneaded but also the speed at which the dough is kneaded. For example, you could knead the dough on the #1 setting of a Kitchen-Aid mixer for 15-20 minutes and the dough should turn out just fine. There will be little oxidation of the flour, little damage to caretenoids, little rise in the finished dough temperature (due to frictional machine temperature), and little damage to the gluten. But kneading the dough at, say, #4 or #5 speed, for a much shorter time period, could undo everything, and you could end up with a tougher dough that results in a tight, dense crumb rather than a light and airy pizza crust.
On the other side of the coin, too little kneading, however achieved, may result in a dough that 1) has poor fermentation properties (because the ingredients have not had sufficient or proper intermixing), 2) reduced chemical activity and delayed fermentation (because of poorer hydration), and 3) insufficient gluten development. Gluten does not exist in a vacuum in a flour. It comes into being only when kneaded with water. I suspect that underdevelopment of the gluten will result in a dough that is of uneven quality, with poor rising characteristics (poor gas retention), and hard to handle and shape when you are ready to use it. A longer fermentation/retardation period may cure some of these ills, purely through prolonged chemical reaction, buy you would never do this intentionally when there are far better ways to make a good dough.
No matter what machine is used, or what techniques are used, the trick is to stop the moment you achieve the desired results. You have mastered the technique for your particular recipe and your particular machine. That should become your personal benchmark from which to conduct future experiments. The best thing about having found what works best for you is that you can always return to it to make a good dough. For a lot of people, that has been a real struggle to achieve.
Peter
