>It is even worse when the existing developers are expected to train the new >developers and then they are laid off so the new developers can have their >positions. It happens all too often...

Here happens the same, after 5 years hard working developer is tired.
Usually we move them to management(project manager) or support possition or training/teaching one. Experiene of this developers is valuable and NOBODY can afford to lose it.
Two developers(MCP) of my accounting team after finishing of new verion signed a Ph.D. degree and said that they like two years rest. They come and support other part of the team, but I understand them. The preasure was very high.
In reality fired skill developer is real competition. Many managers do not pay attention to this.