Flares go a long time for my kids as well. I would also like to figure that out, among many other things. At the heart of it, I am of the opinion that something else is driving Pandas as I dont see any family history yet both of my sisters have P kids. Its one or more of diet, plastics, pesticides, glyphosate, vaccines, EMFs or who knows.
The frustrating thing about Pandas is that what works for one person doesnt necessarily work for another. Both of my kids did a T&A without any success, in fact it was after the T&A that we went into the worst flare.