I'm 15 years old and topped out at 96mpw this summer, with several (4 or 5) weeks at 90+. Last summer I hit only 66mpw as a peak and was more around 55-60 for the majority of the summer. I can't speak for long-term effects yet obviously, but as far as short term goes its done wonders for me. I recently PR'd on a difficult course, my first race of the season, on a week of 87miles. My previous PR was set at the (blazing fast) state meet last year. So the point is that if high mileage works for you, which it might, then high mileage really works. Some people can achieve what I do on much less, but I am fairly certain I could only achieve it with more.