As for the whine on decelleration. The motor you have is split phase and uses a centrifigal switch to disconnect the start capacitor (housed on top the motor). As motor winds down you will normally have that whine, followed by a click as the switch actually trips back to the closed position. As for motor life span the switch and capacitor are the weakest components. Where practical avoid rapid start-stop cycles. Baldor motors are common and repair parts are not very expensive. You did well at $50 for that motor.