Most machinery doesn’t like to sit idle.
Nothing kills an outboard motor like just sitting.
This is true. That said, aircraft maintenance is really some of the best in our history. Also, these flying machines were built to be serviced in every way. Remarkable.
Grimly, they will probably test them in the air when the economy comes back, using passengers and crew as guinea pigs.
I heard the old SR-71 Blackbird leaked fluid constantly when in the hangar. It was built to withstand the conditions of extreme speed.