I am in the 2nd week of phase 2 of the cool impossible. So far things are going pretty good. I am looking to do a half marathon this fall/ winter, but because of family, schedules, etc the one I found is about 4 weeks after I am scheduled to end the cool impossible run foundation program. If I repeated the last 4 weeks of phase 2, would that be the best way to train for this? Should I keep the heart rate training zones concentrated on the half marathon training zone?