This will be a bit "embarrassing" to admit to, but I tend to not use much of my exercise phys background (Master's from Ball State, plus one added year of study). At that time, I was running 70 mpw, and ran a 2:55 and 2:54 marathon within 6 months of each other, and was age 32-33. Hard days (intervals or hills) T and Th, race some Sats and long runs Sunday.
These days at age 67, and still working 30+ hours/week on my feet, I am running about 30 miles/week, varying from 25-35. Long runs can be 10+ miles and intervals once weekly, if at all. This summer's heat and humidity kept us from feeling like doing much work at the track at all. My log from the last couple years has including how many hours of running/week and any elliptical work. On average, I'd say that I have ABOUT 5 hours/week of running, and that is keeping me at my same 150#, and then 2 x 30 minute upper body weight lifting to add. My runs tend to be 3 to 5 miles during weekdays, a bit more on weekends.
I'd race, but doing that in heat/humidity, then work? No thanks. So spring and fall racing. Point to all this is that I just run the pace that feels good for the day, whether 9:30 pace, or 11:00+. I find I need two days of recovery, minimum, for hard efforts, and don't use a heart rate assessment, except at the track, races, and for the long runs, and that is only after the runs to see what I know, that it was a hard effort.
I cannot imagine running 10 hours/week, I'd be so exhausted I could not get out of bed, but maybe that is cause after 41+ years, this is what my body views as it's comfort zone. And I don't want to fall asleep while waiting on a customer or watching "Late Night".
Yes, I am hoping to be competitive in next month's 1/2 marathon and then some 5 km's after that. And I hope that I can get in a longer run this weekend of 13 or 14 miles to feel more ready for it. Would like to go longer, but seems that that really hurts my recovery and fatigue levels. So I may go a bit too easy on myself with "listening to my body" and not practicing my science better, but my aerobic base gets tempered with my "living the rest of the day well" base. Or maybe I should have just gotten that Master's in Psychology instead of Ex Phys!? :) :)