I adore Insanity but I was in good shape from running before I started it, and it was hard going to begin with. I have completed 4 or 5 complete sets of it and now tend to use random workouts as a standalone exercise. It's sort of my fitness minimum standard if that makes sense?
The first month workouts are around 40 mins, the second month ones are upto 60 mins. They start with a warm up that is more intensive than a lot of cardio workouts then there is a period of stretching (some basic yoga etc) then the workout starts...My fitness shot through the roof and I felt amazing, I have continued onto both volumes of Asylum (same trainer) and now also enjoy Fitnessblender for strength.
You may prefer T25 or Max30 (by the same trainer), the workouts are shorter and have a modifier. Same high standard, same fun!!
Having done insanity, max30, T25 etc, I agree with awful - fitness blender might be what you're looking for. I find insanity itself not sustainable over a long period of time as the workouts are just a bit too long and full-on (you have to be very fit to get through them), and the shorter workouts a bit repetitive after a while. They are all very cardio heavy, which for me is not as efficient as strength training. Haven't looked back since I found fitness blender. I swear by Kelli's strength training routines, for which you only need dumbbells.