Final answer:
Brokers are commonly required to maintain records of rejected offers and expired listings for 3 years to comply with real estate regulations and for auditing purposes.
Step-by-step explanation:
The period of time that a broker must maintain files of rejected offers and expired listings is specified in real estate regulations, which can vary by jurisdiction. However, in many places, the standard duration for maintaining such records is 3 years. This requirement ensures that brokers have a historical record of transactions and interactions that can be reviewed for compliance with real estate laws and regulations. It's also important for potential audits, disputes, or for reference in future dealings.