According to the Canadian Standards Association (CSA) Model Code, which has been adopted into PIPEDA, personal information should be retained only as long as necessary to fulfill the purposes for which it was collected. This principle ensures that personal information is not kept indefinitely without a valid reason, supporting data minimization and limiting potential privacy risks associated with unnecessary data retention. This principle is reflected in the CSA Model Code's retention guideline, which emphasizes the need to retain personal information only for the duration required to achieve its intended purpose. Therefore, the correct statement is Option D.