well no components can last forever! and if there stored in high heat areas it WILL make the electronics fail more frequently! Also just because you let or store your engines for long periods of time is not actually good either because capacitors can dry up internally especially if stored in extreme temperature changed hot to cold or freezing , to plus 130 degrees F or cold to hot.
the more often you run your electronic the better because they come up to normal operating temperature ! some failures you'll get is w hen you store your engines for long periods of time and if there is a cold solder joint from when the engine electronics was made may not show up but because the temperature swings you get in storage expands and contractions the cold solder joints have opened up enough to make the board not function. that's why you might have a again that you never ran but stored in temperature changes environment ! and it does not work the next time you open the box and it wont work! both Lionel and MTH have both sold many engines that have cold solder joint that fail. and no components were defective just a cold joint !
one of the reasons why the first ps2 5 volt boards failed was the components were driven to there maximum current capacity. the amplifier were driven to overload. if you ran ps2 5 volt boards to max volume and while starting up you could see the current increasing while during startup or PFA announcements, if you turn the volume down a little then it was ok!