Isn't valve adjustment a scheduled maintenance item?>>>
Not so much now as it was years ago. My sister had to have them adjusted every 15k miles or so on her 81 Civic wagon.
Incorrect adjustment can lead to burned valves, but that's true for leaving them alone>>>
Having 'loose' valves is much better than having too tight a lash adjustment.
e as well as adjusting them wrong. If you're worried about doing it wrong, take it to a dealer or mechanic.