What are you talking about specifically? If the threat is zero, why am I still milling around keeping people in my peripheral view? If I have the occasion to remove myself from the conflict zone, I probably will. Immediately
Sure, the possibility of a secondary combatant or additional danger could always be possible and should probably not be forgotten. Again, unless I am surveying the scene as I am leaving.. I am not sticking around to watch the badguy or wait around for his buddies to show up. A call to 911 and a rendezvous with authorities may be in order but standing around a hot scene is not what I plan to do.
Whether I reload on empty or tactically during an ongoing incident will depend on several factors not some arbitrary rule. In every case? No matter how many rounds are left? Nope, I do not share that sentiment.
I always want a full compliment of ammunition on board because part of my early training drilled in the concept of "Be Prepared"'
I do not want to be over whelmed by the remainder of the pack of hyenas while rendering first aid to myself or my target (assuming I won the initial engagement).
My moral training dictates that while I should have no qualms regarding the defense of myself , loved ones or the innocent, I have responsibility to save life whenever possible if it doesn't threaten my own safety, loved ones or the helpless innocent.
Making the call to authorities only comes into play as a first course of action should the attacker run away.
If my target is able to run away after a handgun battle and I have made substantial center mass hits, I was carrying too small a caliber (weak) weapon.
That too falls under the heading of "Be Prepared".
I believe folks who advocate carrying truckloads of ammunition on board and in spare magazines (i.e. ultra-high capacity) usually at the root, have little faith in:
1. their own marksmanship proficiency and/or
2. lack of faith in their choice of caliber and/or ammunition
In my opinion, for whatever that's worth, it is of little consequence to be able to make substantial hits and still have my antagonist able to continue to stay in the fight.
I hope this better explains my position.