| Because the chrome on the rockers is no more than a few thou' thick, if it does start to flake and lift off the effect on the valve clearances is negligable.
As Philippe says, by the time it gets bad enough to start getting noisy, the rockers will be so badly worn, your cams will be knackered to.
You can get a "visual" indication by looking at the leading edge of the rockers contact patch where the cam hits and you will see the cams' start to lose their black finish, but the only reliable way to inspect them is to pull the cams.
It doesn't take long and isn't too difficult.
The alternator nut is again a pretty easy check.
As Marty says, if it has come off you will be able to see the flywheel moving through the inspection glass, especially when you thumb the starter.
Another "check" is to pull the clutch with the engine running. This makes the "rumble" easier to spot if it's there.
Again, the only reliable way is to pull the engine cover off and check it that way.
There is a new nut available now, which is better, but still not 100%.  | 
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