Transfer from DLA to PIP went better than expected

After being on higher rates for DLA indefinitely for such a long time I was dreading the transfer to PIP.
I suffer with extreme anxiety (as well as spondylolisthesis) and so my husband made the initial phone call to DWP for me as I become extremely panicky when I have to deal with anyone on the phone.
They basically forced me to speak to them on the phone to confirm certain things by saying that if i didnt the claim couldnt be initiated which was really upsetting, and made me dread the rest of the process.
But from then on it was easier... forms arrived quite quickly, then within a few weeks I was advised I would have a home visit, which sent me into a total panic!
But the lady who visited me was very nice, and although I knew from past experience that a friendly face can not always be trusted under these circumstances, the home visit went ok and although I got stressed and had a panic attack, we managed to get everything done.
The home visit was at the beginning of august... today I got my letter to say that i get enhanced rate for both elements from october 2016 to july 2019, so thats nearly 2 years 10 months.
I am a little confused by the award time period as i was under the impression that it was meant to be either 'short term' for up to 2 years or then 'long term fixed' for 3 to 5 years etc.... my award time period seems to be in between, so not sure whether that means that they expect my condition to improve quite soon, or whether it falls into the 'improvement possible but less likely' category... does anyone know? many thanks

thank you so much gordon, your advice is really appreciated.
To be honest, I think that some of the points i was awarded were too low, especially since i made sure i stressed certain points both on my forms and during my home visit.
for example, i stressed that i need help to get in and out of the shower, but was only awarded points for using an aid in the shower.
also, i stressed that i cant prepare a meal without supervision and assistance, but was only awarded points for needing prompting to prepare a meal.
there are several more examples of this that i wont go into.
i am assuming (maybe incorrectly) that if i had been awarded the points that i feel i should have been scored, i would have been given a longer award rather than 2 years 10 months.
dont get me wrong, i am happy to have been awarded enhanced rate until 2019, but i feel that a longer award would have been appropriate in my case.
if i knew for sure that more points would have increased the length of my award i would probably argue the point, but if it wouldnt make a difference i dont want to rock the boat!