Response time make and break customer relationships. Not just customer relationships, but any relationships, be it professional or personal. But interestingly all non responses are not because of tight schedule or a because of being busy, sometimes they are intentional.
Lack of knowledge on the responding side is a strong reason for non response to questions. A delay is chosen over an “I don’t know”. Many times the person does not want to respond, plain and simple or you are not in his or her priorities. Understanding responses is key to managing relationships (at least on a professional level)
Respond fast if you can, it makes a lot of difference to the receiver