PIP reassessment

I have had a number of cases recently where clients have been successful at PIP appeal but in the follow up letter the DWP have put dates, significantly ahead of the date Tribunal have put for award to end, when they will contact client to check still eligible. In one case award ran until 2022 but date to look at again was within a few weeks of successful appeal. Is this something other people have seen? Is it something that could be challenged as it seems to undermine decision of Tribunal.