Started in October and finished the full 60 days at the end of December. Two days after I finished, went to Killington and was bombing hard from 8-4 for three straight days and believe it or not... I was neither that sore nor tired. I felt I was beyond mid-season form at the very beginning of my year. It was unreal. Some of the people I was with thought I was taking speed on the side and they were in their mid-twenties... I am 31.
It's intense. I was doing cycling classes 2-3 times a week and going to the gym a total of 4-5 days a week for various workouts so I was in decent shape before I started, but it still totally kicked my ass. Do as much as you can and try to stick with it. In the beginning, I was taking plenty of rests, but by the end of the first month, I was completing the whole workout through and through with barely, if any rests at all... then came the second month. It's WAAAY harder than the first. I could barely finish the warmup, particularly due to this one exercise where you're in a somewhat push-up position and you have to kick your legs up in the air as far as you can.
Watch out for the plyometrics. Some exercises you can get away with being a little tired and not having the best form, but with any power jumping (or any variation thereof), take a rest of you feel tired. My wife injured her knee a bit not resting during power jumps.