Insanity is only 2 months. It is very cardio intensive, and I use it as a "cutting" workout. I then follow it with P90X (3 months) which is resistance training intensive, and I use it as a "bulking" workout.
Many do both workouts simultaneously. I think they are crazy!

I kind of like the swap back and forth as it increases the muscle confusion.
And Insanity isn't completely devoid of upper body strength training. Level 1-3 drills are tough. I can bench 350, but it was a rare morning I could keep up on Level-3 drills.