I've only ridden a Dahon folder, but I had the same misgivings as you about using it for a long tour. When I saw that the Pathlesspedelled folks had given up on the Bromptons and didn't seem to do many miles on them in NZ I took it as a confirmation of the issues folders have on long tours......I might be reading too much into that, but the options for packing a regular bike are pretty good if you keep the weight down and plan ahead.
IMO, Dahon's are crap. Bromptons are good folders, but they're designed for quick folds and short trips, not long distance touring. Bike Friday makes high quality folding
touring bikes. They're not cheap but I have more than recovered my original purchase price with all of the airline fees I've avoided. I've toured in various parts of the world on my Bike Friday, and it rides like my "regular" touring bike. If you do a search in the forums you'll find dozens of testimonials, maybe hundreds.
I've never had a problem finding a place to leave the suitcase for my Bike Friday while I was touring. On the one occasion when I was flying home from another city, I converted the suitcase to a trailer with the hardware I bought from Bike Friday. I was impressed with how easy it was to do.