The time Twelve O'Clock High is about is before the time Memphis Belle is.
If you watch TOCH you'll see the original commander complaining that his men needed to know there was a limit to what they would be asked to do. The answer was, "We're working on that."
By the time the Memphis Belle events occurred that limit had been set. Twenty-five missions. If a bomber aircrew completed 25 missions they got to go home. Up until the crew of the Memphis Belle did it, no one else had made it to 25 missions. In fact, at that time, the average life expectancy of a bomber aircrew over Europe was 13 (yes, thirteen) missions. The average life expectancy of a bomber air crew was 1/2 the number of missions they needed to survive in order to come home.
I read an article once that said here were over 80,000 US Aircrewmen buried in military cemetaries in Europe/Britain. Think about that one. There were raids over Europe where up to 60 bombers were lost. With a crew of 10 that meant 600 men shot down. Six hundred men, in one mission, captured, wounded, missing, dead. In a single mission.
If you watch TOCH, near the beginning you'll hear a radio transmission from Germany with an English traitor spewing propaganda (I believe he survived the war and was hung by the British when he was captured). He makes the comment, "I wonder who talked you into daylight bombing. It wouldn't be your friends the British, would it." Yup, the Brits tried it, lost so many men and bombers that they gave up on it and moved to night time bombing of Europe/Germany only as ineffective as that was most of the time, they couldn't affort the losses they sustained from daylight bombing.
Hell of a movie. Hell of time to live during.