Health Assessment

Hello all,
Just a question on how often a medical assessment (including the war and peace pro forma they send) should need to be performed/completed?

My (shortened!) timeline is as follows;
Nov 2011, esa declined. Appeal with help of therapist to Accept and support group.
Oct 2016 Medical assessment - modified to work group (because I used the furniture whilst waiting...their words)
Feb 2017 Medical assessment form recieved so I called up and they told me I have to do one if its been sent?!

All I have done in between the Oct 2016 and now is attend two brief work related meetings at local office.

Any thoughts?