Well I owned a US Duo from launch until I sold it last year and never had to repair it. I checked the box claiming I still owned it.
I bought a Duo R broken and then had to fix a few things on it.
I would mostly chalk up the reliability of my original Duo to me owning it. I very very rarely break stuff. Obviously no amount of care can keep, say, an Xbox 360 alive, or keep the capacitors from leaking in a Duo, but it makes iPods, phones, NEC systems, etc last a lot longer if you are just nice to them.