What mechanical stress would be that?
Mirrorless seensor take light all the time unless one close the lens with the plastic cover, hence his short life.
Mechanical stress like dropping the camera. Stuff happens.
Is there any data about short life? Is it the same for CCD and CMOS sensors? I take good care of my cameras and keep them for a long time (5+ years). Short life (3-5 years) would be an issue for me. Especially if the "life" is defined as, say, 50% drop in sensitivity, color accuracy, or whatever critical parameter there is.