Do you have any figures? In Soviet service, Merlins barely lasted 60-70 hours.. Allisons the same. Thats for early war engines with less strain. Of course conditions were bad - but the same that Soviet and German engines were exposed to!
As you said, there is a huge difference between short flights with high percentage of high power regime, and long flights most of which is spent at cruising or below rating (rather more typical for escort flights or CAP for Western fighters late in the war).
As you said, there is a huge difference between short flights with high percentage of high power regime, and long flights most of which is spent at cruising or below rating (rather more typical for escort flights or CAP for Western fighters late in the war).