In the case of Dahon, you might have to be willing to wait three months every time you need a part. That's my experience with the hinge on my Speed. I've just replaced mine for the third time, and I've just discovered a crack in the frame. Just ordered a Brompton (which, ironically, is going to take them three months to build, but if it's reliable and they're quick about shipping parts, as my LBS assures me, it'll be well worth it).

http://www.youtube.com/watch?v=4yFuWUydduM