>You better watch out he doesn't allocate your boss's job to himself in 1.5 years!
>

Words to work by:

Don't be irreplaceable. If you can't be replaced, you can't be promoted.

Here at where I work we used to have people the wouldn't share their knowledge thinking they had job security then. I personally don't believe anyone isn't replaceable. It might hurt for a while but someone still step up or you might learn that you didn't need that information in the first place.