I've still got a JCP microwave from 1982, a GE made with Toshiba parts. When I got it, I singlehandedly pulled the thing in its box from the hatch of my VW Rabbit. Today it's all I can do to nudge it around the countertop for cleaning. It weighs a TON. Big enough to contain a fullsize turkey, though who in their right mind would attempt to microwave a turkey? Took it halfway apart 4 years ago, the stirrer motor developed a nasty squeal that a drop of oil fixed.
What appliance of ANY kind can you buy today and expect 30+ years of service? Geezis, the fluorescent display is still bright and the clock dead-balls accurate (it's an industry term) (My Cousin Vinny).
I only 'cook' meatloaf, scrambled eggs, and hamburger (browning dish) in it but I heat EVERYthing from vegetables to coffee water. I can't even guess how many hours that machine has on it.
But back to JCP as a whole, they were mom's utility clothing source and their branded stuff (whoever actually made it) was good as any. Not so sure the same can be said today, mostly haven't been there since 1982. Which might suggest their problem.