I'm not worried about his large number of carries in high school at all. It's not even close to having a big workload in college. When you're that young you heal very quick and like others have said you don't take anywhere near the beating as you do in college.
I hesitate to even say this bc I don't want anyone to think I'm "that guy" or bragging in any way bc I'm definitely not (I'm usually the one laughing at people who brag about high school sports). But anyway, I started at RB and LB in high school and my senior year I average around 35 carries a game and, for the most part, the next day I usually was barely even sore and the only thing I did was take an ice bath after games. I say this to try to make the point that at that age the # of carries aren't really that big of a deal. You're not taking hits from college level defenders on every play and you heal so quickly that it's not like being the workhorse for your college team. I don't know if anyone will find this helpful/relevant (probably not) or anything but I just wanted to share why I'm not worried about the "mileage" Reid will have coming in to UT.