The 1st month workouts are all around 40 minutes or under. The 2nd months workouts are all closer to an hour.
I workout first thing in the morning because it just fits my schedule better. If I wait till later I find too many other things to do instead.
Good luck and I found that for the first month, it helped if I did a quick 5 minute warm-up before his warmup. My 5 minutes on the treadmill was sort of a pre-warm up. He does warm you up really well and then you get a really long stretch (6 minutes) before he works you really hard. The extra long stretch seemed a bit strange right in the middle of the workout at first, but I learned to love it and even look forward to it. For me, I was used to a more gradual warm-up, which is why I tacked on a pre-warm up for the first month.