Does your treadmill let you set the pace for the "intense" workout? What I have seen in the past is you can manually increase the difficulty and it will still run the same workout, only instead of a 3mph walk as the baseline it would be maybe a 5mph jog and work up to a 7 or 8 mph speed portion and then back down. Another thing is that the program may have been designed around a 1 hr time frame, and it might not condense down to a 20 min workout well. I don't know what the capability of your treadmill is, but those are a couple things I've seen when I've used various treadmill workout programs in the past. As far as bringing up your miles next week goes I would keep the first few days of the week the same, since that is when a bulk of the milage is going on, and if your body responds better towards the end of the week you can extend one of those workouts to add more total miles. I've recently started stretching again after running and I'm surprised how much faster it helps my legs recover, so if you aren't doing that it might be a good idea, especially after long runs where your legs are keeping a constant tempo for an extended period of time. I only spend about 5 min to do quads, hamstrings, groin, calves, and back.