The most basic or simple BPPV is when it is clear from history and it is recent. A young to middle aged adult with a clear posterior canalithiasis BPPV is normally 1 session, maybe 2. This is the most common condition. Lateral canal treatment is tough and an cupulolithiasis treatment becomes much more difficult.
However, I don’t think that is what we are referring to. As otoliths generally dissolve over a few weeks or months and can naturally migrate out of the canal, I believe that we are talking about a sustained central nervous system response…though by that time it is hard to know if an otolith is still present or if it even ever was.