"when they need it"...? not sure what the manual says, but I'd guess it depends on what type of rocker nuts you are using (gm, old or new?), or 'lock nuts'? and it probably depends greatly on how you drive it. the only issue I've ever had was when I tried to use 'lock' nuts, because if the locking part looses, the rocker looses very quickly (bent a push rod in my case), and the same thing happened to my son in law when he used the after market 'locking' nuts'. So I prefer 'new' friction nuts from GM... and if they need adjustment, you won't break something, you'll just maybe get a little clatter which tells you 'time to adjust'...