Currently reminders are sent only to those invitees who have not responded to a survey. Would it be possible to develop a system whereby those people who had not completed the survey be issued with a reminder (with a different text to the non-respondents). I would envisage this would be either: a. Those incomplete invitees who had not responded to a sufficient number of questions (LastResponse < question x, where for example x = 75% of way through survey) or b. Those incomplete invitees who had not responded for a certain period of time (CompletedDate + x days)
Having reminders only go to respondents who have not yet opened the survey and not to those who have partially completed the survey was a big problem for us in a 4000+ respondent study we ran. I would rank this high in priority for the Invitation Manager.