You are correct that every shot is unique. My buddy's boy shot a huge doe last year through the lungs big enough you could easily stick you thumb through it. The doe and the 8 deer herd she was with had been spooked by other hunters before being shot. When she was shot the other deer took off, she followed them for about 150 yds before dropping over. I think she ran that far only because she was trying to keep up with them and she already had adrenaline flowing from previously being spooked. This year he shoots one and it drops over in 30yds, it was by it's self and calm.
Something else to think about, seems a lot of people want to make a heart shot. There was a study done I believe back in the 50's where during a Firing Squad Execution a doctor attached a EEG to the prisoner to see how long there was brain function after being shot in the heart. He put a bullseye over the prisoner's heart for the marksman to aim at. He found there was brain function for 6 seconds after being shot in the heart with the existing oxygen in his blood. If you think about it a deer can go a long way in 6 seconds on a full run. So the heart is not necessarily the best place to aim. Through the middle of the lungs with the heart still pumping, with that amount of Vein and Artery damage you induce shock, severe and sudden drop in blood pressure (which you wouldn't get with a heart shot you would still get blood pressure drop not as fast), blood is not getting back to the heart very well to be pumped into the body, but it is coming from the body to the heart to be pumped into the lungs, you create a bilateral pneumothorax (both lungs colaspe) with a entrance and exit hole they can't breath, plus drowning in their own blood being held in the chest cavity.
Not that we can intentionally do this, but if you hit the deer's lungs on the exhale when there is the lease amount oxygen in the deer's lungs and you create that bilateral pneumothorax deer can't breath in and will die even faster. DANNY