Early 30s, not married/no kids, full time job, full and active social life. I ran 70 - 80mpw for a few years with pretty strong times in 10K and HM. I guess I would consider myself a local standout. I ran two marathons but they were pretty week in comparison to my shorter races. So last year I committed myself to marathon training at 100mpw. Jumped from 80mpw to 90-110mpw over 2 months by adding an extra double and adding a few miles on to most of my runs. Never ran on Sundays. Not for any religious reason, I just like to party on Saturday/Sunday and hate running with a hangover. I held this for about 3 months with an average of 98mpw. A typical week looked like this;
Mon AM- 8 easy, PM- 12 easy
Tue AM- 16 hard, PM- 5 recovery
Wed PM- 10 easy
Thu AM- 12 hard, PM- 5 recovery
Fri PM- 8 easy
Sat AM- 22 hard.
Sun- Off
Total: 98 MPW
I work full time but I'm salary and have a flexible schedule as long as I get my job done. Show up at 7am, work for a bit or hit a morning meeting, head out for my morning run around 9am. Eat lunch at my desk or have working lunch meetings. Usually leave around 5 or 6pm and do my evening workout. That's a 10 or 11 hour work day but I take a 2+ hour workout break so it evens out to about 8 hours of work a day. I could work less but I'm kinda an 'up and comer' and I take pride in doing my job well.
Even though it was 'only' one extra run and 25 extra miles more per week the difference between 75 and 100mpw was huge for me. My fitness shot up almost immediately. PRed in the 10K and regularly held HM pace over the last half of my longer hard runs. Unfortunately I was constantly exhausted even with 7 - 8 hours of sleep per night. I never wanted to go out any more, I was winded walking up the stairs (yet strangely a 10 mile tempo didn't phase me), and my body hurt all the time. Like, really hurt. I called in sick one day because my legs just couldn't get me out of bed and I stayed there, awake but not moving, until 1pm. Then I went for a run.
I developed a minor case of plantar fasciitis and milked that into 6 weeks off. I was just burnt out. When I came back I stayed with 70 - 80mpw and I feel much better. Serious marathon training is not for me.