If your timezone is different to your host's that can contribute to the delayed responses of tickets & emails. Also if your dealing with a smaller scaled web hosting company you'll probably find that they are busy assisting others.
Taking those factors into consideration you should generally expect to receive a reply within 24 hours.
I noticed someone in this topic mentioned that anymore then a few hours is unacceptable for the answering of support tickets, yes that maybe the case if the host a person is dealing with operates on an international basis & has multiple employees. From personal experience unless the issue is of great significance and a company is operational in it's office and is not closed, support tickets are answered in under 5 hours if not 24-48 hours.
If you suspect that the support team are ignoring your query why not give them a call?