Perhaps an anomaly and knock on wood, but my son and I have an Aragon amp bought used in the early 90's, that is still running strong. Two newer, but still old Aragon multi-channel amps are doing likewise. Alas, a Phase Linear 400MkII amp bit the dust a decade or so ago, but it was "born" in the late 70's. However, the last time we fired-up its companion pre-amp, it worked seemingly fine. And a Pioneer tuner from the late 70's remains going strong.
Yet to change the subject a bit, computers, smart phones and tablets etc., seem to have more limited lives not due to hardware failures but due to Operating System and program and App advancements. For example, we have a Zenith IBM compatible computer from the early 80's, that still boots from its huge 30MB hard drive and runs the programs designed for it.