I've only been flying for about 8-9 years, but I haven't been bit, yet. Not bragging and I have gotten into the back of a prop while turning a needle valve, but not more than a couple drops of blood. I think the main reason is that while teaching kids, we exaggerate everything dealing with safety. We even walk around the front of the plane so that we remove the glow ignitor from behind the prop. It's now a habit that I use all the time, teaching or not.