I've had my P3P for a couple of months now. Healthy Done says I've had 90 flights with a total of 13 hours in the air. I'm not seeing any cracks anywhere, but with the forces imposed on the props I'd imagine once a crack develops it would quickly turn into a break, throwing the rotor out of balance, imposing greater stress on the remaining props and having a possibly cascading effect downhill from there. So it seems prudent to rotate the props out at some interval before a problem develops. Is there a best practice for this?