I'm over 70 and fortunately in good health and still able to lug around either a couple of MF's and lenses or LF field camera and lenses. The posts though made me think that before scrapping all the heavier equipment ... is it possible to rig a monopod with a wheel or a luggage cart with a monopod perhaps as a handle. I think a machine shop could handle a conversion.

http://www.jeffreyglasser.com/