A person probably won't run out of bullets but time. Never enough time. Extra ammo is simply more time to stay in the fray. Distance is time so work on recognizing threats early. BBI and Cedartop can help with that lesson. Putting a firearm into action takes time and some carry methods are not as fast. Missing is most definitely time. Misses take time and create liability. Don't miss. No such thing as accuracy by volume. If you do carry a single stack sub compact (like I sometimes do) especially under deep concealment keep in mind that time is your enemy.
Another thing to add is to practice with ammo that is similar to your carry ammo as often as possible. Too many folks practice with WWB or other light loads, then load up with +P for carry. This is one area that hand loading helps with, in that you can load ammo that's close to your carry ammo, yet is cheap enough to shoot a lot of.
BBI's stats have convinced me to focus on those first three to five rounds and make those as effective as possible. To that end, I'm willing to give up on capacity for an improved caliber. But, the G30 kind of lets me have both. It gives me 10+1 rounds of .45 in a package that can be taken in 80% of the places I go. I've got options that gets me most of that last 20%, but I've found little downside to the G30.