Determining when to dispose of data and reducing review costs
The legal (but somewhat impractical) issue is pretty straightforward here—what industry you’re in will determine the regulatory and legal requirements for you. Since relatively few industries are subjected to substantial regulatory/legal requirements for preservation, the question of retention of most records is, often, a balance between the benefit of end user access, aka knowledge management, contrasted against the burdens of data retention expense and potential legal production obligations.