Same with me, I've been training 9 years...can't do the splits and can only JUST reach my toes when im fully warmed up. That being said I can easily perform head-high roundhouse kicks and can do well-over-head-high front kicks.
I can't remember any serious injuries i've received, maybe the odd corked thigh... The only injury i've caused is when I cracked 2 ribs of a 2nd kyu with a knee kick, accidental force of course.
How does a belt get dirty anyway? Your not supposed to roll around in the mud with it on. The theory behind not washing the belt is that all your hard work and training and sweat goes into that belt and washing it demolish's the hard work and such. And you'l get people that say belts don't mean anything blah blah blah...the truth is a belt should mean more than just something to show your rank or grade.