I've replaced mine twice at slightly over 20k miles, and both times it was too dirty. I'll have to shorten that interval to about 15k, which means this fall, if the snow ever melts here in MN. I did ride about 40 miles on Saturday in 36 F heat
to get my bike to the trailer taking us to Austin for this weekends MotoGP. It was worth it.
Don't know how you are able to get the filter out with the outer plastic in the way. On my 08 it didn't seem like there was anyway to do it. Maybe my hands are too big or I'm klutzy.