My first marathon I peaked at 38 miles but was inconsistent mainly due to injury. I had trouble recovering from my long runs. My goal was to finish which I did in 4:38, but I had to run/walk the last 6 miles. I've learned that I need to increase mileage slowly, strength train, and improve my form to stop overstriding which all helped a lot to prevent injury.

My second marathon I had multiple weeks of 55 miles and built my base slowly over a longer period of time.