I think that 1.5 hours exercising is a bit too much. Most people tend to recommend at most 1 hour per day, including warm-up (so this means 30 extra minutes of sleep :-)).
I think you'll find a wide range of times works for folks, depending on what sort of routine and exercise you do and stick to.
If you love road biking, you will probably spend more time exercising then someone who loves doing a lot of high intensity interval training and cross-fit style workouts, simply because of the nature of the workout. You can ride bike for 3 hours easy when you are in shape, but there is no way you can do intervals for more than 45 minutes unless you are nuts.
