Couple of things:
Obgyn, there have been, I think, a fair number of threads on ESRPlanner here. Interesting tool and theory. I've tinkered with it a fair bit.
I agree with many who say that travel, especially international travel if desired, might be best done early in retirement, saving the "easier" trips in the USA for later life, simply because the older we get, often times the less adaptable we are to sudden changes and disruptions, of which travel seems to have more than a fair share of.
I traveled for a couple of weeks to New Zealand in 2003. My flight was around $1000 back then, and Air New Zealand coach was positively luxurious compared to domestic US flights. I'd put a return trip there high on my list of places to go, but only when I can stay for longer. The nonstop was from LAX to Auckland.
I love reading about perpetual travelers, but know it isn't the life for us. We need/want a home base, something to return to, and a place that is embedded in our psyches and peopled with our friends and family.