I've been flying my Spitfire for 10 years now, and still going strong. I think that once you're pretty experienced, say about 2 years, most crashes are caused by some componant failure. Like a servo fails, or a piece of wood breaks, or a screw vibrates loose. There are a million things that can go wrong. But if you inspect your equipment every few flights, you can catch a lot of these problems before they cost you.

I always tell students; it's a great sport for breaking stuff!