In principle, by the methodical order itself, a few minutes is enough.

   Really, according to statistics, one half an hour working session is enough for the half (50%) of all pacients.
   One more working session (shorter than the first one, 10÷15 minutes) is necessary for the half of the rest (25%) pacients. Next half of the rest (12.5%) needs next more working session and so on

   Therefore the most of working time is a test period, which a pacient needs to make sure,
        he/she is satisfied with the obtained result,
        he/she is indifferent to that, what suffered him so far
    Duration of the control period is individual. Occasionally it takes weeks, but mostly everything becomes clear during the first (astronomical) day.

    The separate problem, pedagogical one, non-psychological, is to learn how to live normally, like one learns to walk after he wasn't up for a long (weeks) time.