PIP Assessment 1 year early

I was awarded PIP 2 years ago, up until March 2018. But i had ''How you're disability affects you'' form 3 weeks ago and was notified today that I have a medical in 3 weeks time.

Firstly, does the original award dates that they give mean anything anymore as i am being accessed 1 year early.

And secondly, since being diagnosed and although successfully treated for head and neck cancer 12 years ago, its left a nasty trail of endless physical and mental disability problems for myself, I have had to claim DLA/PIP since then, and although my health and disabilities has deteriorated over the years, does there actually come a time where its plainly obvious to the DWP that i will not become better, although they still insist asking for endless medicals? Is that normal?

Thanks in advance

They shouldn't say you have an award for three years or so because you clearly don't have it for that long