I don't know when I will be assessed for PIP - I have an indefinite DLA award and have done for years; only got reassessed downwards because i asked them to, and wasn't expecting to have to be reassessed again 
Mind you it was the same with IB - I was essentially supposed to not have to be assessed again for that, and they still made me claim ESA and put me in the WRAG - so after a year, I had no more ESA
(I tried to appeal but they put it through as an application to be reassessed and decided I'm support group, which means that while I got my ESA back, it wasn't backdated to cover the period I had no money).