Okay, Druydess I think that's true of any stallion that what they produce should dictate how much they produce. Than again we have the case of Impressive where the genetic mess that follow his success as a sire was not found until years later. It seems an inherent flaw in the breeding of horses that you start breeding next years foal crop without knowing much about this years crop. Lets say you have a stallion who does very well in his discipline. He is bred to 20 mares and sires 20 foals. The owners "like the look" of these foals and those twenty mares are bred back, along with twenty more mares. So at the end of two breeding seasons you have sixty foals out of one stallion and none of those foals have done anything to indicate that they are healthy, sound, trainable or going to out-perform their sire. Many issues that limit a horses career don't show up until that horse is 5 year or older. Its only a serious deficit that prevents a foal from eating, drinking, peeing, pooping and being cute which is basically all people really expect a foal to do. So, in those cases you can have a horse cover a large portion of its breed without actually knowing what he produces.
The true mark of a great stallion is that he out produces himself. The problem is that most stallions have produced themselves so much that you don't know if its the odds or the horse that are the cause of the greatness. If you produce enough foals eventually one of them will do something correctly. So, do you think changes should be made to limit how many mares a stallion can cover in the first few years of breeding?