The only time I turn over the propeller by hand is when the Flight Manual or Pilot's Handbook says that I should.
I don't remember reading in any Piper or Cesnal manual that the engine should be rotated by hand prior to flight.
Many people justify the hand turning of the prop as "limbering up the oil" or "breaking the oil". That is basically rubbish according to Piper and Cessna........if it is cold then there are two requirements....a) Use the correct grade of oil and b) Use pre-heat if necessary (very very cold temperatures).
I fly one type that the flight manual requires the prop to be turned by hand prior to first flight in order to check compression. I do this only prior to the first flight and while the aircraft is chocked and tied down.
So basically unles the flight manual requires hand turning then don't do it because.........if it chops your hand off (or worse) or even if it runs into another aircraft, the first thing the insurance company will say is you should not have done that so we won't pay.
Regards,
DFC