I haven't changed the plugs or adjusted the valve lash during the 19,000 + miles my 954 has. It still runs like a top. How much wear have you guys found when you pulled your plugs? Also, have you had to shim your valve lifters?

The service manual suggests that you replace your plugs @ 32,000 miles.
The valve lash, on my machine, was fine @ the 16k service interval... right on the upper end of tolerance. I'm very satisfied with my 54.
I actually bought my 54 because I worked in a Honda dealership and I liked the way they did things. Not the fastest on paper, but the most reliable!!!!

I would not bother to check valves until 32k. I have heard of no one who had to shim them before that mileage. JS

i changed my plugs at 20,000 miles and they looked like total crap. that was a hard 20,000 miles though :D you might want to take a look at em though.