Question: how many miles per week to run a sub 4 hour marathon?
Answer: A 4:00 hour marathon is approximately 9:00 per mile. To break 4:00, you should eventually be capable of a sub-1:50 half-marathon (8:20 per mile) and sub-50:00 10K (8:00 per mile). Right now, you should be running at least 20 miles per week, and be able to run for an hour non-stop.