Some folks do silly things like train with mouseguns for 25yds. and 1911's for 3ft.away.
So you should carry two guns? One for long distance and one for close up? At what distance do you decide to switch from one to the other? So, if an attacker jumps you from 4 feet away, and all you got is a full size 1911, you can't shoot him? If someone runs at you from 50 feet away and all got got is a Keltec P-32, you have to wait until he's on top of you? I think not.
You simply train to hit what you aim at with whatever you've decided to carry from whatever distance you think you may need to fire.