But 50 minutes is a chunk of time, even for advanced runners. Go too much farther in a tempo run, and you lose some of the speed benefits of the workout. Even after this training program is completed, you may want to keep a tempo run of about this length of time in your training repertoire. Along with the interval training programmed for Wednesdays, tempo runs do the most for maximizing potential. Wimps don't belong.
Tough training comes with the territory.
Most important is to get out and cover the distance at a comfortable pace. It's not easy always to find time to run close to an hour a day, but it's essential if you want to achieve a peak performance. I have your longest run planned for you over the weekend. That being the case, you might want to skip the 3-miler you might otherwise have done today and opt for complete rest. You might experiment with the meal you plan to have the night before the Shamrock Shuffle.