Marc Bloom, in his Harrier xc newsletter, would survey the Foot Locker finalists and ask about their training. He's no longer publishing the Harrier but I had a chance to see that particular issue the last 2 or 3 years. My recollection is that very few of the guys were doing much more than 60 miles per week, although there were a few. What you don't know is how fast they were doing those miles and how difficult the terrain was, etc, and what sort of workouts they were doing as part of their training. 60 miles a week can mean anything from jogging to doing intense workouts, tempo runs, hill runs, etc.
My kid was a very successful high school runner and never ran over 55 miles per week, and he was always getting asked about his workouts and mileage. But he would always tell people that what worked for him wouldn't necessarily work for them - he did the same training as several teammates and none of them ever achieved his degree of success. One thing that always stood out for me about my son, however, was his consistency. Most of the kids would be erratic over the summer and the winter, but he was always rock solid, almost never missing days except for taking a break at the end of track season for 2 weeks. He also was super careful about diet and sleep and all those 'little' things, and a lot of the other kids were not.
60 miles a week sounds great to me, if you can handle it without injury and without burnout. Make sure to do a long run once a week, in the 12 - 14 mile range, as part of those 60 miles.
My kid also ran a lot on sand, including sand dunes. I'm a believer.
Good luck.