It depends on "where" you are doing business. If you have an online site most people expect you to respond within minutes.  In addition to my Agency, I have a Promotional Product business -- key chains, coffee cups, etc. I have lost business because I did not get back with someone within 30 minutes. I am a fairly small business and I am not open at night and on weekends. I have had an inquiry at 2 o'clock on a Saturday afternoon and when I followed up at 9 a.m. on Monday they had already gone with someone else.

Clearly, the Internet has changed the way we do business.

I will say, how you respond is as important as the time.  I have people that want to be contacted by email, text, and some still by telephone.  I am not a big text guy. In fact, I hate to text.  But I love email. It has been a challenge for me to use text.  But for my clients that want to use text, I have learned.