Six months of support is free, just so you know. Sounds like you may have bought an additional six months to give you a year.
As for the response time, although there are exceptions, most themes are created by individuals or small teams that may not have the facility to provide 24 hours support. If they work standard business hours, and you were to contact them at 5:10pm, then it wouldn’t be out of the ordinary for you to get a response at least 16 hours later.