In my Project Management class I touch on this subject. It is to get the point across as to how to act as a manger. We are all replaceable. Someone held the job before us and someone will when we leave or retire. It is our responsibility to do the best we can with the position we hold and to turn it ver in good shape to our successor. That said, while we are replaceable, we are also valuable. Any employer who feels they can just drop someone into any slot at any time is a fool. There are good people who do make things go. When we lose them, we lose loyalty, production, experience and knowledge. Those are difficult things to replace. So it is a balancing act that both the employer and the employee must respect and deal with. If not, both lose.