A lot of people who own guns have not shot them in years. That doesn't make them a non-shooter, however. That being said, I think they are probably kidding themselves if they are counting on effectively using a handgun in self defense that they have not shot in years. They might do fine, but from what I have seen of people who have not shot in years, especially those who didn't shoot much anyway, they don't do that well. I have seen some of the folks qualifying for a Texas CHL that had to unload the hollowpoints from their gun that they loaded in 4 years prior when they last qualified. Even at 3 yards, they get some wild bad shots and the qualification shoot isn't high pressure at all.
I would not suggest people should not be allowed to have guns if they haven't shot in years or don't shoot at all. I am just saying that I would put more stock into me performing a tracheotomy on a person with a collapsed airway like I have seen done on TV on the Lifetime network than I would on the non-shooter doing well under stress, say in a home invasion scenario. By the way, I am an archaeologist, not and MD.