The Jumo 004 engines were as good as they had to be; with flight time of only around an hour per mission, 50, or even 25 hours was enough for quite a few battles. Germany did have a shortage of the more expensive alloys, the prototype engines used them and lasted longer, but for production purposes they were downgraded so they could be made cheaper and quicker; the high temperature areas went from nickel to aluminum coated mild steel for example. They were far cheaper and easier to manufacture than the radial or V12 piston engines on their other front line fighters, and the time between overhaul was a good trade-off. That, and the ability to run on lower grade fuel made them popular with the Luftwaffe high command. 8,000 of these engines had been built with production continually ramping up - 1,500 per month by the end of the war, with 100,000 per year planned for 1946.The ME262 I saw at Oshkosh last week was a full scale reproduction not a restoration. They said the reproduction aircraft used the same engines as Lear Jets. The engines on the Messerschmitts were not good at all. They had a predicted service life of only 50 hours but in actual service often only lasted 25! The Germans during World War 2 either didn’t have the technology or the access to the metals needed, or both, for their jet engines to have quality metals that could last long in high temperatures.