Two year old documents

I have been on higher rates of both PIP since 2013 and my current award comes up for review in 2019. I have a plethora of medical diagnoses of issues that have stemmed from a Significant Traumatic Brain Injury and several Strokes in 2010 that caused an early retirement on ill health. My last submission included a summary of all my problems and how they collectively affected me psychologically and physically. This was a comprehensive medical report from a Clinical Psychologist in Neuropsychology. This summary was after an extensive set of tests of several hours over about 6 weeks. This report is now over 2 years old and will be even older when my next assessment becomes due. Does this mean it is inadmissible, even though it states there is no expectation of recovery but only further decline? If the DWP will not accept it I will need to begin the arduous process of getting a referral and waiting for availability for another slot for assessment by the Clinical Psychologist. It seems like an unjust impediment to expect a claimant to have to go through such a demanding and arduous challenge at every assessment point. I am 65 and my conditions will never improve but are certain to deteriorate. It would take many months to be able to provide reports from all my consultants. So does a clinical report lose all its relevance after 2 years as far as the DWP are concerned? Regards Lew