Real planes use metal props, but turn them at much lower RPM. They have log books and strict inspection and overhaul points based on number of hours of operation, which is basically the number of revolutions of the prop.

How many guys log exactly the run time of their engines?

The forces on a prop that matter are fore-aft, not along the blade. If the engine were always pointed directly in to the wind, the force would be constant, but it isn't. If the engine is even a fraction of a degree off from the direction of flight, then the blade at one point of a revolution has a higher angle of attack than at another. That cause more lift and more force at one point than another. This cause the blade to flex a little as the force increases and decreases. That's like bending it back and forth with every revolution of the engine.

There's a world of difference between 1,500rpm and 15,000rpm when it comes to blade life.