Why assume unlimited time, money for practice?
If time or money are issues, you have to go with what's realistic. Nobody has ever proven that he could reliably hit the chest beyond about 25 yds, while he was actually being shot-at. Either they got lucky with a single shot, or they missed several times, proving that the hit was a luck shot.
In the first place, most attacks are not made with a gun. So you can't justify firing much beyond about 10 ft, at most. 6 ft covers about 75% of realistic defensive firing, and 90+% of attackers wont make you shoot them at all, if you get the gun out and "on" them soon enough for them to notice it, and stop their attack. Only 20% of the most doped up, desperate nutcases, facing life in prison for multiple offender armed robber cases, chose to shoot it out with NYPD's Stakeout Unit, in Harlem, late 1960's. More of them probably would have surrendered, but Cirillo and company shot them down before they could do so.
You will not be encountering such hard core offenders. So, 90% of the time, you wont have to hit them with a bullet. Over half of the gunfights occur at less than 10 ft, according to the FBI'S Uniform Crime Report. So about 99% of the time, you won't be firing beyond 10 ft. That's the reality of justifiable civilian defense with guns. 90% of the time, you wont fire at all.