The failures I've seen are the heating element dying (annoying in one fridge because of how it was wedged in, real pain to replace), the drain pipe clogging (this can be really annoying to clean), or the computer just giving out (usually takes the whole fridge, but I've seen it just lose the defrost).

All three are more annoying to deal with than a fridge where you just know you gotta defrost it now and then (chest freezers still had that for longer, maybe still do).