Yes, those guys are maniacs, for sure. In a good way, of course.
It's also worth noting how dangerous this tree climbing is. One mistake, and you are gone. I think everything over 92 feet they call "the death zone". And these trees don't have low limbs, so sometimes in order to climb one tree, you have to climb a smaller one, and then jump over.
Then there is the case of the notorious adventitious branches on the lower trunk. These branches can easily break, and become "widow makers".
It often happens, that in the middle of a climb (that can last for hours) a ferocious storm breaks out. Some climbers can actually tell from the noise that tree makes during a windstorm, whether or not it is about to snap or topple. These are really terrifying moments, if one happens to be in the middle of it all.