If you run a 100 mile week then 80 miles a week is 'resting', if you run a 130 mile week then 100 miles a week is 'resting', if you run a 191 mile week then 130 miles a week is 'resting'.
Think of training as peaks and valleys. Think in both micro (day to day, hour to hour, week to week) and macro (weeks to weeks, months to months, years to years).
Stress the body (hard workout, high mileage week/month/day, new type of workout, etc). Heal, repair, adapt, while maintaining fitness (easy easy day, lower mileage week/month/day, same old type of training). Stress the body again (harder workout, higher mileage, etc).
If you do the same thing over and over again you'll get less and less of a benefit. Simple adaptation theory. You also have to push the edge, sharpen the blade, then back off, repeat again but push harder sharpen more.
Remember when you first started running an hour a day? It hurt didn't it? Remember your first time running doubles. It hurt didn't it? Remember your first mile repeat workout, your first marathon, your first 5k. It hurt didn't it? Does it hurt now? Is it difficult now? Probably not.
If you've been maxing out at 70 miles a week for 4 years in a row now and have been running the same types of workouts would you really expect to improve?
The marathon is a 26.2 mile race. For the best it will last between 2 hours and 2 hours 30 minutes. It is a test of endurance and stamina. 191 miles is 27 miles a day. I bet he doesn't have any issues with the distance when he races a marathon. If you never or rarely put in more than 2 hours a day how you can expect to run well for 2 hours and 30 minutes on race day?
Alan