I don't know why people are giving a hard time and not answering. Basically running 45-50 miles a week is not hard for a highschooler, any random junior and senior that hopes to run a decent time should be doing that in the summer. Obviously there are things to worry about (injury, the pace you are running etc.) but basically you are going to be better off the more you run.
I ran about 45-50 miles a week before my senior year and ran a 16:20, nothing special by any means, but faster than your current PR's. I fully believe that dropping my PR 30 seconds compared to my junior year is a huge part because of the increase in mileage.
I went on to easily running over 100mpw (built up of course) in college, and earned NCAA all-american honors in XC, I was nothing specaial in HS and put together a respectable career.