I rarely run unless its pointless to continue (turnfighting A6M's in a Fw190D or simmilar situation) and even then i come back and do some more damage or need to change my position to help out a squadie. The only time I truely run is if I have damage (such as engine oil, or fuel leak in my last remaining tank) that doesn't allow me to continue to fight.
I don't deny that your a better pilot than I am, but it all boils down to expierence. I'm a relativly new player. And it depends on your plane. If you say you can beat my P-51D in a P-39Q, it may be so, but I doubt it would be as bad for me as you say. Unless there are rules somewhere that say a fight is over if the fighting A/C are more than 1.5K distance from each other, then if we fought, I would use my advantages for all they're worth. Only an inexpierenced pilot would hold off on using advantages unless intending to lengthen the fight.