If you must use deadly force, you'll always be better off only using that amount of force needed to stop the threat
While this is true, be aware that YOU might not get to decide what is "sufficient" force. It might be a jury that decides that, one instructed by a prosecutor in his "version" of events.
This possibility is compounded by the current preference for high capacity semi autos, speed shooting, and the actually valid advice to "shoot until the threat ends".
Generally speaking, most people don't recognize the threat ending until the attacker falls, or runs away. Even with a "stopping" shot, it may take a couple of seconds for the attack to fall down, and while on their feel, they are still a possible threat, so you keep shooting.
A relatively skilled person can rip off up to a dozen shots from a 9mm in a couple of seconds, and relatively unskilled person can often manage half that in the same couple of seconds.
Which can lead you to having a prosecutor demand you explain to the jury that, since the ME testified the deceased was shot 10 times, and only two of the hits were incapacitating/fatal, WHY DID YOU SHOOT HIM 8 MORE TIMES!!!???
Go ahead, explain it...we're waiting....
(the only valid answer to this loaded question is "you shoot until you know the threat is over (immediate threat). A counter argument is to challenge the question, pointing out that you didn't shoot 8 more times, when you didn't NEED to, you shot until the threat ended. After all, how do you know it wasn't shots# 9 & 10 that were the ones that ended the threat??)
In the past, many taught the double-Tap, shooting twice, then assessing the threat to see if more shots were needed.
This has fallen out of favor, mostly because it decreases one's odds of surviving a gunfight. When you stop shooting to "assess" IF the threat is still there, you might be taken out.
All a matter of personal risk assessment, and the situation. If you've got a bunch of trophies from winning shooting matches, you're going to be looked at differently than someone who bought their only gun "for protection" last week.
It shouldn't matter, but it does.