I responded to the survey to say waiting until later made things worse. I think the best thing all programs could to is release as many interviews as possible as early as possible, to prevent people from going on interviews they don't really want. For example, I got offered interviews at two programs that I wasn't thrilled about, but at the time, I only had 8 interviews total, so I wasn't going to turn down those invites. By the time I had enough invites that I felt comfortable turning programs down, it was 2-4 days before those interviews, so I couldn't cancel. So essentially I ended up wasting two spots for other people, because other programs waited longer to tell me I had an invite.