Ours is a mere child, born in 1994.
But we have a Cuisinart, vintage 1977, that we use at least once a day on average and it is still going strong, except that the bowl, which is slowly disintegrating, seems to be irreplaceable. New Cuisinarts are very hard to use and to clean. They have been tied up, surely by liability issues. Stupid morons cannot keep their fingers away from a rotating blade.
I’ll chime in and second what’s been said-usually, it is the timer/disply module that goesw bad. If the oven has a Amperex/Philips magnetron, that tube will last decdes or more.
Which is a pity-if you cannot get a display module, you have to junk the oven.
That’s the beauty of having a 1976 microwave. Display modules weren’t invented then, so they can never go bad. Mine’s got a simple dial that one turns to the desired time. All mechanical. Then when it clicks over to zero a (also mechanical) bell makes a loud DING. Sometimes old ways are really best!
Very well written. This is very, very sad… 
sad flower
Wow–very poignant yet very sad.