In my opinion I would consider the DHF to be a living document. Often times in a products life span there could be changes in materials/processes and its good to look back at historical data in order to compare data sets. I know in my experience I have looked at historical data and compared different aspects of validation/verification of equipment or devices. I have had instances where the DHF wasn’t consistently updated and it becomes very hard to determine what the thought process for particular changes within a process or equipment.

Chris