> Planes still need like half throttle to maintain altitude,

Yes, bit less than half, but anyway that is exactly why I said takeoff would be the peak power output.

> that’s why airplane engines are rebuilt every few thousand hours vs lasting hundreds of thousands of miles (tens of thousands of hours) for a car engine that only uses a small fraction of its power to keep a car moving.

Ratio of max power to average power is very low on the list of reasons why a gas turbine engined plane needs maintenance more frequently than a piston engined car.