"How to keep on the level of *enjoyment of life* on the tour, to sustain that note of invigoration that sometimes happens, and even exhilaration -- which is (or can be) a major part of touring -- without letting it cross the line, into another zone -- one of exhaustion or depletion or some lower level of living.... "
Well you can't. It's like the old Buddhist story where the guy goes to the holly person and spills out all his complaints and finally quietens down enough to ask for the secret to solving all his problems. The holly person says that he can't do anything to help, and that there are 86 problems in life and as soon as you stop worrying about one of them the next one rears up. The supplicant is angry and wonders aloud what good is a Buddha if he can't help him with his problems. The Buddha answers by saying that while he can't help with the 86 problems he can help with the 87th. The supplicant asks "what is the 87th problem?", The Buddha answers "worrying about all your problems".
I wonder if a person with Buddha consciousness has any reason to go touring.
I found this thing on U-tube about a lady who rowed across the Atlantic. As she goes she losses one system after another, and around 100 days looses all external communication. She points out how unfair this is as she had really been planing on calling home for a good "winge" I like that. I know I need a winge back home every now and again... Maybe the advantage to bigger than normal experiences is that at least the pain seems worth it, or possibly for some it may be finally some pain/experience worthy of them. If you have to be in pain why not because you are 'Exhausted, filthy and ill' traveling in Tibet, rather than just rolling through a traffic jam on the way to work.
I think there is some bad Karma listing one's Tibet trips on the China Bike site...