Out of a 2007 RK with 9500 miles. Started out clean and then gray then black. And it really stinks. Pulled apart to install Legends cartridges.

 

Nasty but it is 12 years old. That said what is your question or statement? Makes me wonder what my 07 RK looks like at 20k.

 

Fork oil turns black pretty quickly. I do mine every two years and it's dirty. Between 8 and 10,000 miles.

 

Bought a 06 RK with 40k mi, started sounding as if a broken spring or loose washers was clinking around when riding over washboard pavement. I was freaked, thinking a teardown coming. But first things first, I changed out fork oil and cured the noise.

 

Just changed mine after about 9 years. Not going to wait that long again since it feels like a NEW RIDE after the change. When my front fork oil gets OLD the front end seems to WOBBLE especially when I'm slowing down to a stop.
I'll try it at about every two years and see what happens.