If they're recommending a valve adjustment without having taken a look under the hood then yes, they are just blowing smoke up your a$$ and out your wallet.

What else are they going to do for $400 for the 30k service? I personally think that many of these scheduled maintenences are a waste of money. Many of the parts can be inspected with relatively little trouble and they can use that inspection to determine what REALLY needs to be done as opposed to what is scheduled to be done.

The big exception to this is your timing belt/water pump job. Do you know when that was last replaced?