They seem pretty reliable now. My replacement set has no cracks and performs wonderfully.
Mine are 2nd generation and build quality is quite good. No cracks, loose screws, etc.
BUT....it squeaks when you move the headband/cups like a beginning saxophone player at an elementary school band concert.
Thanks guys! And just to be extra sure about it, cause I live in Barcelona so the climate is pretty humid here, how difficult/expensive would it be to replace those wooden rings in a hifi shop (instead of sending them back)?