when i was an endurance athlete i would only do HI sprinting once every 2 weeks.  the more I did it, the more my body wore down
if you are a sprinter obviously your training will be different.  the facts of the matter either situation is this ridiculous idea that spending 2 hours training a day will yield better results is absurd.  even if you go to the top college track programs, they have their athletes in and out of practice within a short time.