I understand the idea of going from 50 mi/wk to 80-100 making a huge difference.
But what if you're coming from Triathlon, where you were doing 50 running miles a week, but 15-20 total hours/wk of total aerobic work?
If you go from 20 hours/wk of tri training to say 10 hours/wk of strictly running, but at 80 miles/wk, will you still see improvement? Surely one would see improvements in running economy from all the additional easy miles?