It is not a BS argument, people NEED one hour of exercise per day to be "healthy", but not "OPTIMALLY healthy". Three hours of cardio is better for you than one hour of cardio, A LOT of people get zero hours of cardio everyday. A man that exercises for 1-3 hours a day has a higher life expectancy than someone who exercises less than 1 hour per day.
I disagree. 3 hours of cardio every day is way, way too much...even for my friend who is an ultra runner. He only runs 3 hours once a week (1 hour on other days) most of the time yet consistently places top 5 in ultras (50 - 100 mile races). When training for a race he may run 6 hours, but then takes a couple days off.
I believe in quality over quantity. This is what I do:
Cardio:
5 minutes slow running to warm up, 20-30 minutes alternating medium to hard running (or biking) at varying speeds or intensity, 5 minutes to cool down.
Lifting:
Day 1: Upper body day. 8 sets of compound pushes (after warmup), and 8 sets of compound pulls with medium to heavy weight (6 - 10 reps). Total time - 30-35 minutes. Compound pushes are either bench press or incline dumbbell presses. Compound pulls are either weighted chin-ups or rows. I don't waste time on single muscle exercises such as curls or triceps extensions.
Day 2: Lower body, same thing 8 sets of squats, lunges, etc., and 8 sets of deadlifts, good mornings, etc. Total time 30 minutes. Again, I don't do any single muscle exercises like leg extensions or calf raises.
I alternate cardio one day, lifting the next day, then cardio, then lifting, and so on. I miss the occasional day, but average 5 - 6 workouts a week. My results: At age 53, at 5'7" and 170 pounds, exercising about 30-40 minutes each time, I can run a 5k in 21 minutes, bench press 260, squat 380, and deadlift 410. I can also do 30 consecutive chin-ups.