You often mention exhaustion here. What do you think of regimens like those Pavel Tsatsouline recommends, like those discussed in this Joe Rogan clip for instance. I.e. do however many reps you can, not to exhaustion, so there's always fuel in the tank, so you can do more overall. So it's like a lower intensity but longer lasting kind of exercise.

Secondly, any thoughts on whether lifting weights does away with the requirement for cardio? I once read something along the lines of: if you lift weights, your muscles grow, and those muscles will need to be maintained 24/7 by your heart, so your heart will need to be stronger 24/7 instead of whatever amount of time a typical cardio lasts, and that overall is either superior or equally good as typical cardio. Also, in nature we seem to follow this rationale: no one run marathons in nature, but they worked low intensity for longer spans of time.