I have an '01 YZ250F that's had a Scott's oil filter in it the whole time.
After wearing out chains/sprockets, at least 20 sets of tires and riding hard for years, the engine compression is still perfect. (Same as new 04)
I've checked the valve clearances a few times and they never went out of spec. The engine runs so well that I've never even bothered to take the spark plug out -even just to look at.
I attribute this longevity to the Scott's filter keeping the motor perfectly clean. By the way, I'm not one of these guys who changes oil after every ride - or 2nd, 3rd, 4th, etc. I only change it when it starts to darken in color - which takes awhile.
You bet another Scott's is going in the '04!