Final answer:
The Ordo Decurionum was a council in the Roman Empire, with membership often held for life depending on local laws and individual competency.
Step-by-step explanation:
The Ordo Decurionum was a governing body and local council of the Roman Empire, which consisted of wealthy and influential citizens in a Roman city, who were responsible for the administrative and religious affairs of their community. The term 'Ordo Decurionum' refers specifically to the order or rank of these council members known as decurions. Duration of membership in the Ordo Decurionum could vary, and there is no specific universally applicable answer, as it depended on the tenure defined by local municipal laws and the individual circumstances of the members. Often, membership was for life, provided the decurions met the requirements of wealth and social status, and fulfilled their duties competently. If a decurion failed to meet these requirements or was involved in misconduct, their membership could be revoked.