I checked the valves on my '04 CRF250 today, a little over a year after I got it. Original valves, shims, everything. I have only ridden maybe twice a month, so probably 40-50 hrs. total is all. left intake - .006" right intake - .005" , both in spec right exhaust - .011" left exhaust - .011" , both in spec I was happy to see it was so, because even though both my '02 and '03 CRF450's stayed in spec for a year, so many seemed to have unexplained problems on the 250 just like the 450. Maybe I'm just lucky? Don't know. All I know is what I do, which was the same on all 3 bikes. After the first couple oil changes, I run Mobil 1 red cap in the engine and Honda HP Trans oil in the tranny. I change oils every three rides, oil filter every six. I change the air filter about every three rides also, but I do it by sight and how dirty it is getting. One thing I DON'T do is ever change my filter at the track. When I change mine I do it in a very clean garage, and I clean out the airboot immaculately before I re-install. I see guys changing filters at the track, with dust flying everywhere and I just cringe. Some of that is definitely going in and you can't stop it. Does this make a difference on valve recession? Don't know, but mine have held up for three full years on three different bikes. On riding style, I wring the snot out of this little bike. I race Vet int., against mostly 450's, and I will rev it out until it doesn't make power at least once a lap. I don't think I'm abusive on it, but I don't baby it either. I use third gear everwhere I can for as long as I can. This may mean nothing, but I just thought I'd give a 'what I've done' on a bike that has lasted very well and doesn't even need an adjustment a year later. Take it for what you will.