The school of thought that says that the DHF is sealed at the end of Design Transfer is most appealing to me, and that is the school of thought that my company follows. We have quite a large product portfolio, so if we had to update every DHF every time we updated any SOP or our design control procedures, I think we would be spending almost all of our time updating old DHFs for products that are currently on the market rather than focusing our efforts on developing new products. As new procedures and updates to our design control procedures are rolled out, we implement them in new projects, but we do not go back to old DHFs to assess whether they comply with the new procedures.