I prefer what Gerry Weinberg said
In the Psychology of Computer Programming he said that if you notice that someone is irreplaceable, fire him immediately. Eventually that person will leave, and the pain will be greater later than it would be immediately.
In the 25'th anniversary edition he said that over the years he had received more thank yous over this piece of advice than any other he had ever offered.
Cheers,
Ben
I have come to believe that idealism without discipline is a quick road to disaster, while discipline without idealism is pointless. -- Aaron Ward (my brother)