How long are Xinjiang police not allowed to work?

You can stay as long as you don't make mistakes.

Contract police usually sign contracts once every three years or once every five years. As long as you are willing not to make mistakes, you won't be fired.

In the recruitment and management of auxiliary police, if the relevant administrative organs and their staff abuse their powers, neglect their duties or engage in malpractices for selfish ends, the directly responsible person in charge and other responsible personnel shall be punished according to law. If a crime is constituted, criminal responsibility shall be investigated according to law.