LTD insurer keeps requesting "updated" medical records every 60 days even though my condition is permanent - is this normal?

I have been on long-term disability for almost 2 years now for a chronic condition that my doctors have all confirmed will not improve. Every 60 days like clockwork I get a letter from the insurance company requesting "updated medical records" and a new attending physician statement.

My doctor is starting to get annoyed because nothing changes between these requests. She literally writes the same statement over and over. Last month she charged me $75 just to fill out the form again. Is this constant requesting normal or are they fishing for something to use against me?

I keep complying because I am terrified they will cut me off if I miss a single form, but i feel like im being harassed. Has anyone successfully pushed back on this or is this just how LTD claims work forever?