I've been doing it for 2 months, as I had a shytty back, bad knees, i'm only 25
I'm in shape muscle wise anyway as i've been lifting weights and eating right for 3 years, but I gave the weights up and focused on recuperating my body.
Never felt better, back is stronger, knees are stronger, core is stronger. This stuff really works
The average time is 30 mins, apart from his main workout called the Diamond Cutter, go figure, which is just under an hour and is the hardest cardio workout i've ever done.
Integrate it with your weights and you're laughing.