I had my cranks mounted by Roland Wende (municycle.com) when he assembled my KH29 and since then I never touched the screws. He used locktite, and the screws didn’t come loose for ~ 500 km. Unfortunatly the “test” ended here because one of the bearings gave up (not the knurled one). I don’t know what torque Roland uses, but it looks like his method works very well.