Agree with the idea that you don't know your limits until you reach them. When I was in job training for the Army we did PT every day. The XO for our company lead PT, and he was a beast. Tons of running, tons of walking lunges, tons of pushups and ab work. At first I didn't lift while I was there because the PT was so intense, but after a while I said screw it and started lifting every day. I would go after we got released and work either lower or upper body, alternating days, but taking no rest days during the week. The work load was enormous, but I had already adapted to the PT volume and my muscle memory kicked in for the lifting side of things. I never got too sore, and my lifting never seemed to interfere with my PT.
No one could just jump into that level of volume if they were untrained, but it was fun to push myself and see what I was capable of. Most people have the view of "what can I take away from this workout while still getting results". I see things like "what can I stand to ADD so that I can get MORE out of my session". If more people saw things this way I think a lot of people would get a lot more out of the gym.
Raw gym PR's, soon to be broken-
Squat- 435 (405x3)
Bench- 345 (315x2)