Final answer:
Client files are typically maintained for at least 3 years to comply with legal and regulatory requirements, offer clients access to records, and provide evidential support for potential legal disputes or audits.
Step-by-step explanation:
The recommendation that client files be maintained for at least 3 years upon their completion date is primarily related to complying with legal and regulatory requirements. Keeping these records can serve as important evidence in case of legal disputes, audits, or other regulatory reviews. It also provides clients with access to their historical records for personal or administrative use. However, the importance of record retention extends beyond just compliance; for example, engineers keep detailed notebooks that can prove invaluable for reviewing designs, obtaining patents, legal defense, or substantiating work hours. Similarly, in other fields such as anthropology, archival records of collections are crucial for future research and for validating historical claims.