So after my first 90 mile week about 2.5 months ago, I did a hard 10 mile run at 627 pace in pouring rain with a 600 last mile. Today, I did a hard 10 mile run on the same route in perfect running weather at 617 pace with a 546 last mile. Only a 10 second per mile pace improvement in much better weather makes me question the high mileage. It may be fun to only run once a day and do 60 mpw so I have time for other things, but do it all sub 7 pace with twice weekly 10 milers at sub 630 pace. The high mileage is kind of tough mentally because its intimidating to be like "oh crap, I have to go run another 8 miles later today." Wouldn't a high quality approach work? Then I can put off the high mileage for a couple years and build up gradually like most people here are recommending, and if life gets in the way its not that hard to wake up a little earlier and sneak out for an 8-12 mile run in the mornings.