67 mile week - Quanity or Quality?

      I put in a solid 67 miles of running this week, about half on trails and half on roads, and I find myself asking if quantity or quality is more important.  Today I finished a 22 mile run with an average pace of 10:00 minutes per mile and the majority of my runs are consistently coming in at that pace.  I found myself surprisingly fresh at the beginning of the week when I knocked out 10 miles at an 8:47 pace.  This felt especially good because it was just 2days after my first long 22 mile training run of the year.  Then on Saturday I felt fresh again and finished 12 miles handily at a 9:12 pace.  Still these times are very slow compared to the paces I would normally training at if I were going for a marathon PR.  During Marathon training my long runs would be 8:00 pace, my slow runs would be sub 8:00 pace and my tempo runs would be around a 7:00 pace.  However, since I am putting in so many miles in a week, my legs are far too tired to being able to hold anything near these paces right now.

So the argument is, would I be better of putting in less miles but making them better quality miles at a faster pace.  Right now for what I am trying to accomplish, I don't think so.  My ultimate goal is to be able to go to the mountains and keep running from morning till night at a slow but steady pace.  That is what I will have to be able to do in order to complete the Bishop Ultra 100K this May.  If I can average 12:00 miles, that would be just five miles per hour, for the whole day, I would finish the 62 miles in just a little over 12 hours.  That feat would entail running on tired legs for more than half of the day and that is what I am trying to do with my training.  Many days when I go out my legs are already tired from the get go.  Even if I am only going for a 10 mile run, it feels like I am running on legs that have already put in more than 20. In addition to learning to run on tired legs, my secondary goal in putting in so many miles is to lose some weight.  Even if I restrict myself to solely veggies and fruit, the pounds don't seem to come off unless I drastically increase the volume of exercise.  I think this is partly due to the fact that training increase the efficiency of your metabolism so you actually need less calories to do the same amount of work the more fit you get. However, even if my miles may be low quality as far as pace is concerned, I strive extra hard to maintain good running posture and form even when I am running on very tired legs.  The type of quality that I am looking for is to be able to maintain an efficient running form even though inside I am feeling like dying from pain and exhaustion.

How about you?  How do you answer your training quality vs. quantity questions?