My friend had a total of 35 or 40 treatment over a period of 3 years. They started out with 3 a week and then started weekly and every other week and finally monthly.
The way I could tell it was working was that by the weeks or month had passed since the last treatment, the symptoms of BP became worse. After the ECT sleep returned to normal and BP returned to less exaggerated.
But medicine was a big part of her therapy and her psychiatrist did a good job of adjusting her meds as needed. Are you on medicines? If not you could ask your pdoc to try that and see if that is more effective.