I never got my normal mileage up to 50/week, so consider this advice from someone that never ran as well as you do. Some readers may not be runners so I will e

I never got my normal mileage up to 50/week, so consider this advice from someone that never ran as well as you do. Some readers may not be runners so I will explain how I trained. I'm not that fast and didn't run in college. I was definitely a casual runner. I kept the mileage under control and that helped me avoid injuries. It sounds like you train harder than I ever did, but I did qualify for and ran Boston. My training was the common seven month training regimen to prepare for a marathon: 3 weekday runs, say MWF, and one long weekend run each Sunday. By the second month I would add speed work at a track something like six 400m runs fast. The three weekday runs were around 3 miles each in the first month and might get up to 5 miles by the time I was ready for the marathon. The long run is basically increased in distance by one mile per week. After I hit 13 miles I would cut back to a long run ever other week, but increase the distance by 2 miles each run. In 26 weeks you was able to do a marathon distance in a long training run at an easy pace. I would work on my speed at the track and the short runs. I would not do any more really long runs once I was 3 weeks from the marathon. After the marathon I would take a few months off and then start again around 7 months in advance of the annual local marathon. By the fifth year I was fast enough to qualify for Boston. So my training was almost all under 40/wk and more like 30/wk early in the season. Having lots of days off let my feet recover. I found that always having two different brands of training shoes helped me avoid the overuse injuries that many of my training cohort seemed to experience. I would alternate shoes each day. This way my feet would at least get some break from the particular way the shoe flexed, etc. I would switch brands every so often--they all felt a bit different. My body isn't ideal for running, so I really had to focus on form: very light footfalls, shorter more rapid strides and no overreaching to keep the wear and tear modest.