Me personally, it takes about half an hour around every run, getting dressed, getting water, stretching before and after, showering and changing clothes. longer runs leave me lethargic for a while. A two hour run leaves me exhausted. A two hour run leaves me worthless for an hour or possibly three.

40 miles in 5 hours is amazing. My bare minimum around running time would be 15 minutes a run, and i can't run 10 6 minute miles 4 times a week. I could maybe do 4 10's@9:00. But if i put in the effort, that would come down.

40 miles at 5 hours/week is just phenomenal. You must have world class biomechanics. I can't imagine how fast you run. You are a stupendous badass. I hope you recover soon.

(As a much slower runner, I can maintain 7:30 for a mile or two. Just not 40. :-))

A very good but not world-level time for the marathon is 2:20 or so for 26 miles. That's more like 5:30 per mile. World record pace is an even more insane 4:41.5 a mile (http://www.runnersworld.com/newswire/dennis-kimettos-maratho...). So yes, 6:30 should be easy, if you're at that level (must be, given that I could do 10k in 40 minutes, which is around that pace, when I was a lot younger, and I'm not a running talent)

The 7:30 pace had my heart rate at 145 on flat ground in cool weather at age 40 for a 13 mile run which from what I understand is the right pace.