I'd add in the "luck" factor as well, Charge, and with very high regards to it.
For instance, I've seen an article quoting the book by Tolliver and Constable which compared Robert S. Johnson, Hartmann, and Moelders side-by-side. The authors note that it took Hartmann 194 sorties to down 28 planes, Moelders 142 sorties, but Johnson only 91. Now, the particular article did not mean any disrespect towards Moelders or Hartmann. It was merely stating the prowess of Johnson as compared to some famous LW aces. Indeed he was a firey, fearsome pilot. But every time I see that article I am compelled to think what Johnson's final tally would have been, if he had to fly one thousand sorties till the war's end.
The improperness of war, (and life as well, I guess) is that Johnson may very well have been shot down and killed if perhaps he flew just one more day, one more sortie. Individual skill and careful tactics increases one's chance of survival and decreases likeliness of being killed during combat, but in the real world "shi* happens". Like you mentioned, Otto kittel, one incident, one day, and bam, it's over. Same holds for McGuire - one more sortie, one more chance for a kill, and bam, America's finest ace augers to death.
When I think of it that way, sometimes I feel the sheer length of time some of those LW aces had to fly, and still survive throughout the war, is perhaps the only thing really important about it all. Compared to that, achieving a certain number of kills suddenly doesn't look all that important.
There's an annual highschool baseball tournament in Japaen called "Koshien" - named after the stadium where the final match is played. This is perhaps the most harsh type of tournament ever in the world of sports - nearly 5,000 high schools competing annually, in a tournament style play where each school plays only one game each round against one school. The winner advances, the loser is dropped out. In order to become the tournament champion, the team has to win every game upto the final championship match. Sometimes it seem an impossible task to win at such a tournament, but nevetheless every year there is a winner. It's just that you can't win that tournament by skill alone.
Sometimes, I think that's how it might have been for the LW pilots. The objective is survive through the war, through some hundreds of sorties. One mistake and you are "dropped out" - literally, from the sky.