I'm not a black belt in any art. I was in an Aikido class and watched a blackbelt test. It was pretty good. He had to show all of his current material, and then a 2 minute stay on your feet keeping moving don't get pinned and stay in control of the attackers randori. The whole thing lasted like 20-30 minutes tops. Now I being where I'm at in the martial arts and the limited experience off and on over the years in different styles I have maybe a unique perspective. I know that physical fitness is important to being able to properly defend yourself, but by the same token most places that I have been too, the tests aren't no 6 hours long. The instructor has seen you do the previous materials for years, and you've worked hard to get to the black belt test. He should already know if your capable of performing these techniques in a life threatening situation or not. IMHO if he doesn't when you test then he probably didn't teach as much as he should have. Perhaps he didn't pay much attention to your previous tests.
I guess really what I'm trying to say is. When your in that situation yes a good run is better than a bad stand, and I know from personal experience, I'd rather get out of there any day. Sometimes you can't. I can't see myself saying, " Wait a second, I gotta stretch, do some calisthenics, a little kata, ok 5 hours later I'm ready to defend myself, now that I'm winded." Course if they actually let you do that, they might get bored enough to just walk away and leave you alone LOL. It does really sound extreme to me. Rangers, Green Berets, those guys need it. ME Not really. I don't see myself ever going 6 hours with someone. It's a macho, I'm a bad dude thing, really. That's not what it's about.
Ok I'm getting myself into enough trouble, but that is my opinion on the matter. Don't be to harsh with me on here. I have meant no offense to anyone. Just stating how feel from my limited experience.