Consumer electronics used to break down all the time 50 years ago. Metal whiskers are not even close to being relevant when other factors impact reliability and durability to a far greater extent.
The consumer devices which survived infant mortality, because they were free of manufacturing defects, had a negligible aging rate after that.
Modern electronic devices have far fewer initial manufacturing defects, due to automated production, but all age much quicker, due to very small component sizes, lower safety factors, surface semiconductor devices (MOS transistors) instead of bulk semiconductor devices (bipolar transistors), lead-free soldering and other similar changes in technologies.
Sounds like you should unplug it before you open it up.
But they could be easily repaired.
Very true, however having full documentation would help nonetheless. My water heater electronic board cost over €250 to replace, although it contains less than €20 parts; a preprogrammed uC makes it impossible to replicate it. If it had public hardware and firmware documentation, someone could repurpose a similar but cheaper board or replicate the functions using a different rugged enough uC board, which would also likely bring down the retail price of the original spare part.
Of course nowadays something that simple could be a chip the size of a rice grain, power included. So that's something :)
Citation required