A few questions from a newbie.... 1. Is there any danger in overheating the motors? I've got three batteries and I like to fly until I've used them up so I play it safe and fly each one for about 15-18 mins before landing and swapping out.. 2. I've had two crashes...both due to pilot error. In one the craft props came into contact with the foliage of a tree. I can see green stains and nicks on the blades so I replaced them. Question is now do you know when a blade is damaged to the point where it should be replaced? 3. Any estimates on how many hours you can put on the motors? Does anyone keep spares around just in case? Thanks for your comments and suggestions.