Physiologically and mentally, how tough a job is the presidency?

True, but I suspect that traveling as a president is probably a lot less stressful than traveling for the average American. You have people to take care of every aspect of your trip, (no need to pack, figure out where you need to be when, wait in the terminal etc), you have a complete bedroom and office suite that travels with you (so you can actually get useful sleep, work and tweeting done on the plane in relative comfort). All you really need to do is just go where people tell you to.

I’m not so sure about that. I suspect that most presidents spend a lot of the flight with staffers, preparing for their upcoming meetings.

Sure, they typically have already been briefed in detail about the issues at hand, but there are frequently last-minute developments to cover. Plus info about the attendees at the meetings, such as “We expect that the head of their Department of Education will be present. Name is Lee Smith. She has four grandchildren under the age of 6. Her youngest daughter is in med school.”

Plus, POTUS has traditionally met with reporters while on the plane. Yes, it’s informal, but still he has to be very careful of what he says.