It highly depends on the type of the business and provided services. For example, technical support has this level of urgency where clients need an immediate answer (in this case a more extensive availability coverage should be guaranteed + high quality self service through knowledge resources). However, most of other businesses should not strive to provide an instant response while setting an expectation to receive an answer during 24 to 48 hours is more than sufficient. If these are long term clients with whom you have regular communication - the secret is to have more productive communication. Write well structured detailed emails, record videos, use async tools, share documentation and FAQs.