Patches,
The tests I ran, mind you they were only for the Typhoon, showed that duration of engine run time was improved by throttling back. What they didn't show though was any improvement in range. Basically, if you had to fly the maximum range then you wanted to run at full throttle (and WEP)... so if you were low on gas, WEP and run for home, don't lean it out and try to cruise back slower. This was basically opposite to what I would have expected but that's what it seemed like at least in the Typhoon.
So, for bomber escort, throttling back would not help other than to make it easier to keep formation with the bombers. It might extend your loiter time, which might be a concern, but if range was the issue then you better just run at full throttle. Typically on escort you are better to keep your speed up nice and high anyway so you can react to things better. Making a zig-zag path at full speed gives you more options to counter the enemy than just throttling up before combat. The only time I cruise in escort at less than full throttle (not WEP mind you) is when I want my engine to cool.. then I cut the engine, reduce rpms, and glide a bit to let the engine cool off quickly.