The main rule in touring for me is that I have to be able to stay comfortable. That is a combination of things, from saddles to gearing, weather to food. If you can stay comfortable you can keep going, in my case some discomfort could be a sign that I was likely to cause myself permanent damage, or it could just be that I was no longer enjoying myself.
While I enjoy ideas like that one should be able to carry a bike, and have been in situations were my safety depended on my being able to clean and jerk the bike over some obstacle, I wouldn't recommend trying these ideas out in the real world. I have hurt myself doing these kinds of tests and they are largely arbitrary so why bother.