When we moved into this house, the wife made noises about replacing the "ancient" oven [0]. I asked "Has the technique of cooking food with heat, changed drastically since the 70s?" We left it in.
When I went to college in 1993, I was given my grandmother's original Amana RadarRange microwave from 1968 or so, the model with the two dials and the "done" buzzer that wouldn't stop until you hit a button [1]. It was huge, HEAVY, and we joked that it was full of lead shielding, but it got used for three years of college and after that was donated to my workplace when I moved to Austin. As far as I know it kept working there for another 2-3 years, and by then was most likely 25+ years old.
[0] https://goo.gl/photos/qrgoixCJDViks8am9
[1] https://i.ytimg.com/vi/hLhXgVAYoAE/maxresdefault.jpg
Addendum: I just realized that the microwave I have sitting in the kitchen was given to us as a wedding gift in 2001. The clock no longer works properly, but it cooks just fine.