Creating depth and redundancy on your team is very important. If someone on your team is irreplaceable, you should be fearful. It is very important to have multiple people trained to perform most functions in your practice. Depth is important for multiple reasons.
First of all, clients want service 24/7/365. If only one person knows how to do something in your practice, then that person will be subjected to being on call 24/7/365. In order to provide consistent service and a positive lifestyle and schedule for your employees, you need redundancy or more than one person with the ability to do every function in your practice.
There are sometimes occasions in which someone at a practice says that they don't want to hand any work over to anyone else. Essentially, they are controls freaks. How does refusal to allow anyone else to learn to perform a task help the practice? The development of leadership at all levels of a practice, along with repetitive capabilities for all tasks will provide job security for more people at the practice. It provides security for the practice to guard against loss of any single person in the practice, and it provides greater ability to provider better service to clients.
Redundancy is healthy for a practice. Nurture and develop the talent in your practice. Create redundancy for every role.