On one of my deployments overseas in the mid-2000’s I was on a search and rescue team in Iraq for a few months. Every night we’d support teams running missions

On one of my deployments overseas in the mid-2000’s I was on a search and rescue team in Iraq for a few months. Every night we’d support teams running missions by getting onto helicopters and getting comfortable for the night. The pilots would spin up the bird and not take off. The blades would literally spin all night long, to the point where we’d need to refuel once or twice(more of actually flew somewhere). Night after night SAR teams around the country were doing the same, for over a decade. The reason why they’d spin up the bird at sundown: these helicopters always had mechanical issues and if you shut it down there was a significant chance the helicopter wouldn’t start back up when you needed it. That’s just one data point in the entire US military but I could think of a dozen others offhand.