Hello,like you I sent my PIP return early December,I included a care plan and a letter from my MS nurse .i made several calls to chase up.I was told on one of the calls that they did not need to see me at all.Then last week letter arrived with decision higher rate for both mobility and daily living,which was a huge relief.I think the info I sent made a difference.i had made a request to transfer from DLA to PIP as my MS had got worse.Hope this helps re timescales ,not sure if it makes any difference what part of the country your PIP is from,in my case North East.Good luck with your PIP application.