PIP increased but only 2 years

Hi, firstly after waiting 4 months, I finally got the PIP review result. Previously it was daily living enhanced rate and mobility standard. Amazed that (thanks to your wonderful site) not only have I kept the enhanced rate for care component but they decided to award me enhanced rate mobility as well!!! Both on mental health grounds

What I don't understand is why they have written 'i have decided to award you this for a longer time's because it is only til 2021 which surely means I will receive another review form in 2020. I have always been given a 5 year award so surprised on the one hand they have decided I need enhanced rate for both yet only giving mean extra year (my current award was til April 2019 though had the form 2018.

I also thought it was no coincidence that literally a couple of days after I got the PIP result, I received another brown envelope informing me that 'due to a recent change' I would continue to receive ESA (in contribution based support group). I haven't heard a thing about my ESA for about 5 years so it was obvious they were just waiting to find out what my PIP result was.

So grateful for your site and all your hard work. Just a bit disappointed that I've got to go through it all again in a couple of years time

They obviously agree that my condition has got worse for them to now increase my mobility to enhanced. That is why I am confused. They have increased my benefit to reflect the deterioration and yet shortened the duration. Can I request a form from them to find out why they decided to award it for two years? Thank you