The three-interview structure works best, in my experience, when the researcher can space each interview from 3 days to a week apart. This allows time for the participant to mull over the preceding interview but not enough time to lose the connection between the two. In addition, the spacing allows interviewers to work with the participants over a 2- to 3-week period. This passage of time reduces the impact of possibly idiosyncratic interviews. That is, the participant might be having a terrible day, be sick, or be distracted in such a way as to affect the quality of a particular interview.
In addition, the fact that interviewers come back to talk three times for an IV2 hours affects the development of the relationship between the participants and the interviewers positively. The interviewers are asking a lot of the participants; but the interviewers reciprocate with their time and effort. With the contact visits, the telephone calls and letters to confirm schedules and appointments (see Chapter 4), and the three actual interviews, interviewers have an opportunity to establish a substantial relationship with participants over time.
Source: Seidman Irving (2006), Interviewing As Qualitative Research: A Guide for Researchers in Education And the Social Sciences, Teachers College Press; 3rd edition.