turnin2,
Just my opinion but this thing is a process that takes the pitcher years to develop to reach higher pitch counts.
There are some who may say that at lower velocities, they can't hurt themselves pitching more, I do not agree. Pitching from the mound does cause stress on the arm regardless of velocity.
The best thing is to follow guidelines set forth for each age group.
If you have pitchers that remain healthy, why change things?