I agree, granpa, ansursvary's right. That answer never varies (only the slightest pun intended, BillK) and is the reason I practice way more than a double-tap to the area of the eyes, nose, and mouth. I've timed this drill with my Model 60. Groups shot with my Crimson Trace sight installed are always at least a fraction of a precious second quicker than my (iron-sighted) point-and-shoot times. In dim light and even at a mere arm's length, the accuracy improves measurably. Especially when packing .38s or .380s, I want to be able to take advantage of the entryways into the skull that don't require a lot of power to achieve penetration.
As to some of my opinions expressed above, they are worth about what you paid for'em. It's just that I have serious issues with some of the principles of "double-tap and assess". YMMV. Please be aware, if you don't live in my county, that a perp shot plumb full of holes may or may not require some courtroom skills that are beyond my realm of instruction. ;D
As to home invasion prevention, we keep a Rhodesian Ridgeback (named Mohawk for his organic hairdo). He teams with an ill- natured female terrier-mix (think Airedale, but smaller). She never naps at night and together, they've proven priceless, whether we're at home or away.
Teeth marks and tears will appear purple and deep
On the calves, thighs, and bruised backside of the creep
By the time he so rudely breaks down my door.
Ol 'Hawk's but one reason I that can be sure
Bloody'll be the creep who dares disturb my sleep.
I ain't paranoid, granpa, I just don't want my old clothes tore up, and you probably knew ****** keep dawgs anyway.
Cherokee