It also can depend on your oil changing and driving habits and care you take of your engine. Adjusting them correctly is most important, I will do mine on every oil change and it's probably a little anal about it.
The manual gives you the simple way in 2 steps. Adjust first set, then rotate 180 degrees and then adjust the next set.
To do them correctly, you need to place the cam in the correct position and adjust them more individually. Only adjusting them when in the center of the base circle of the cam and not adjusting while a rocker might be on the ramp of the cam or worse.
If adjusted while on the ramp, the rocker will be too loose, then the valves will not be as precise when opening and closing. Mine can make some noise, but it is normal noise typical of the non HDL.