For me the initial response time isn’t the biggest deal (and I’m surprised the effect size of a single day delay is so large). What matters more is having a quick turnaround whenever I give you a set of times from my schedule. Companies are so bad at this that I’ve started giving them only fractions of my available time (which makes it harder to schedule interviews). I’m not sure what the solution is because I can’t give you 100% of my available time if you are going to sit on it for three days before scheduling. I’m talking to other employers and need to schedule things with them too.