OP here. Thanks very much to those of you who have responded about my original topic of endurance walking. I really appreciate the links! I'm just in the beginning stages. I've taken walks of moderate distance (6-8 miles) in our area already on a semi-regular basis, but am interested in lengthening those (to the 15-20/mile per day range), and also in taking overnight long walks.
For the overnight walks, I'd prefer ones where I can walk inn to inn, for example, and not carry much luggage (which means packing a daypack with a change of underwear, clean socks, and plenty of water), and I'd limit them to a couple of days for now, and probably once or twice a year at most. That is all I can reasonably think to fit into my current schedule and life.
Long-term, however, I'm very interested in the touring/walking activities I mentioned (Hadrian's wall, and that walking vacation in the Cotswolds sounds awesome, PawPrint 3520!). I also live near the Camino Real (the California Mission Trail) and there appears to be a couple of websites dedicated to walking this route, which is not really a "recognized" or officially sanctioned route yet, so there's still plenty of exploration yet to do, as well as substantial safety issues on the route to overcome (high-speed roads being primary among them).
At Superhero stage, I'd like to walk El Camino Real (800 miles), from San Diego to Sonoma. I am also toying with the idea of walking from Copenhagen to Portugal. I have an endurance runner friend in Denmark (she runs daily marathons -- a marathon a day, every day) so could hook up with her for the Danish part; the Netherlands have a great network of bike trails, I'm familiar with Northern Belgium and can get through there without being on major roads, and am also under the impression that walking the back roads of Europe may be easier than trying to navigate the freeways / highways in the U.S. Especially out here in the West, most of the traditional footpaths have been paved and cars are going 60+ mph -- not a safe feeling for me. Any international Mustachians able to help with that? I'm particularly interested in southern Belgium, France, and Spain. This is a project that is years, probably decades, out, but it would be fun to plan! And if I did it? Massive leveling up points!
For those that are interested in the biomechanics of walking, including gender differences and speed, perhaps starting a new thread to more deeply explore that topic would meet your needs and allow this thread to continue as a source of information / discussion for me as well as others who are more focused on the serendipity of wandering in an exploratory, non-competitive way. I'd really appreciate it.
Thanks, and I'm looking forward to more ideas / learning about the experiences of other Mustachians!