This was a surprise to me:
"While many newer distance runners tend to focus on flashy long runs, the distance of the longest run was not strongly correlated with a BQ. Comparing BQ runners and all other athletes, the distance of the longest run was 20 to 22 miles across each marathon. But, the base mileage was higher for BQ runners, bearing in mind that base volume matters more than the distance of any long run. BQ runners at CIM averaged 65 miles during their peak week, while the rest of the field averaged 50 mpw. Similarly, Chicago BQers averaged 57 miles during peak week, compared to the rest of the field’s 41 mpw peak week."