Should additional duties be considered by your branch for Career Development?

As a unit administrator, I had too many additional duties and not enough time to do them in. Some of those additional duties were relevant to my MOS and position. However, one additional duty required to manage two GSA vehicles. It was necessary for the unit and the facility to manage them, and I had to be the guy to ensure that they were maintained.

Some additional duties should be considered by your functional manager (Air Force Term), and they are for the greater good of the Branch and Career.
For instance, being assigned to monitor Training Ammunition Expenditures and ensuring all of the training requirements are met is a duty our functional states is needed. Then, there is an additional duty for Monitoring Keys and Locks that is just a best practice realized by one of my former supervisors.

This is probably an Army-specific issue. Collateral duties definitely figure into Marine;s professional development.