I heard you'll go blind if you dry fire
Forgive the sick humor. I started shooting handguns in the late 1960s and the general consensus then was that over time dry firing was detrimental to the firing pin and bushing as well as the hammer and frame. Steel work hardens as it beats against the parts without the 'softener' of the primer.
When I was learning DA shooting I used spent 22LR shells in a K22 and would dry fire a cylinder full while aiming at the TV. Swing the cylinder out and turn each shell enough to give the firing pin a new spot to hit. Did this hundreds, maybe thousands of times, and became quite proficient at DA shooting.
This thread has stimulated me to go buy some snap caps for one of my revolvers. Back then I think they were only available for high end double guns. I would like to see if dry firing would improve my skills and I just couldn't do it without some protection for the gun. Even if it wouldn't matter I would rather have the ounce of prevention.