I am trying to find an external referee to review and evaluate an application package for a postdoctoral fellowship. This assessment, which is a required element of the application, is due August 13. I e-mailed a first potential referee a couple days ago (so certainly not very long at all). I introduced myself, identified why she might be well-placed to serve as a referee, and identified the deadline. Rather than following-up, it is likely that I would reach out to another potential referee if I don't hear back from her. At what point do you think I should reach out to another potential referee?
My initial thoughts are after seven or eight business days. I realize this may not be considered a long time for these sorts of applications, but I fear that the likelihood of a positive response will be severely reduced at that point and I don't want to put anyone who does agree to take on the assessment in a position where they feel rushed.
Would value your thoughts!