Hi SL1612,
Yes, I'm afraid that it is DWP practice to start the PIP reassessment a full year before the claim is due to end.
Your son should treat this form in the same way as he did the first one. It must be completed in detail and (copies of) any/all supporting documentation should be sent with it - even if DWP have already seen them.
The decision, when made, will come into effect immediately, it will not be postponed until the expected end date.
Don't forget to make good use of the PIP guide.
PIP help for claimants May I suggest that you bookmark/favourite this on your web browser now so that you can find it easily in future. You probably remember that we prefer to keep all questions and comments relating to one claim in the same topic.