My son is 15u. His high school practices M-F with games on Saturday, as well as during the week some. He is a starter and they ONLY have him pitch a 25 pitch bullpen about 3 days before he starts.
Now, having said that, he long tosses EVERY DAY. There is a huge difference in mound throwing and long tossing. If you want your son to get/stay loose I suggest long toss in proper pitching form.