hello guys, im planning on getting a yz450f this summer.....sticking with blue! my question is in a real world scenario how long do these engines last...im super anal when it comes to maitnence on my bikes...but how long will valve, valve seat, springs, piston rings, all that good stuff last. maybe a few races dabbled in here and there, but mostly messing around type riding. also does the yamaha genisis head have any superlitives over the other brands? thanks for the help!