I've had full remission from HBOT. I had done 80 dives using the professional, hard shell chambers. It was not until dive ~75 did I get full remission. I noticed benefits right away in the first 10, then sort of slowely improved or plateaued for a while, and then jumped to feeling better than I did when healthy at around 75. Massive confidence, lightening quick thinking, huge energy, etc. Full remission and feeling superb was lost when I kept doing the HBOT dives and I think I did too much of it, making me feel worse. But I still had the majority of benefits. I think if I stopped right when I was "cured" it would have lasted for quite a while.
I recently bought a soft shell chamber to do HBOT at home more cheaply than at a clinic, but have been delayed in using it while getting it repaired. It was sort of a last resort move, thinking that HBOT was the best thing that's helped me. Its good to know that some people needed to be doing their dives for several months if not years to see improvement.