Are the XC F valves stainless? How much top-end time can you get on a XC F 250? I've ridden 2-strokes and 4-strokes, like em both, but damn I'm not gonna miss my crf450r on maintenance. Will the mfg's ever listen to riders complaining about durability? I couldn't believe it the first time I saw a two ring piston in a 4-stroke! Is the design always going to be the lightest components, fastest revving, replace often?(A friend just put a $1,000 in a RMZ 450 with less than 55hrs) I know bikes in the past were not as fast but man they lasted longer, I had big bore bikes(even air-cooled) that I rode for years with out rebuilding ***!!!!