As a former firefighter, I would agree with you Donatello to a point. There is a certain amount of extra something that you get when the danger is real. Doing the firefighter combat challenge was the most grueling 3 minutes that I have ever experienced, and as a serious sprinter and endourance athlete, I have experienced a lot (OK, no need for jokes about D&D nerds not being able athletes

).
I have also had 96 hour shifts with no sleep, very little rest, hardly anything to eat, and multiple (most was 5) serious fires interspersed with medical emergencies and technical rescues. The combat challenge is much harder. There is nothing that keeps you going during the combat challenge except the desire to compete. The fires and rescues are actual life and death situations that demand the best you got, for the sake of your crewmates, the citizens, and your wife who wants to see you home at the end of the shift.
Firefighters don't wear steel, but with bunker gear, helmet, axe/pike, air pack, rescue equipment, and miscelaneous tools, you could be wearing 75 lbs! I was the smallest guy on my crew at 6'2" and 200 lbs. Not full plate and greatsword, but about as close as you can get.
Now all that adds up to be that extended "encounters" are not only possible, but the "5 minute rest" could be just as effective if it was a 3 minute ride in a fire truck to a new fire. No offense meant, but LARPing does not really compare well to actual combat.
EDIT: I have realized that my post was probably pretty offensive to Donatello. I want to apologise to him now for being offensive. I was not meaning to be dismissive or potentially seeming derogatory to him or LARPers. I feel that many of his points are valid. What I was trying to do was add that danger can change your endourance. I got a little carried away. I would edit the post, but I think what I wrote was cool for the most part.

I just want to emphasize that I wasn't trying to be a jerk to Donatello personally.