The reality is it takes much longer to access the valves than to adjust them, so that if you offered your dealer/mechanic a little extra to set them up exactly could be $$ well spent.
Mind you, I did this at the 24,000 km service, yet when I did them myself at 36,000 (off warranty) I changed 13 out of 16 shims. Made it run better though.
I'll find out at 48,000 (soon) how well they've stayed set.