Career development
The longer you hold a particular position in the organization, the more you need to consider coaching other people. If you become indispensable, you need to fire yourself from your current position and obtain a new one (in the same company is fine).
This might sound strange to some people, but for the good of the organization, you need people that will grow with it, that will adapt to change. You want people who are up to new challenge. But you also want them to help others, to coach them so that they can grow too.