Your guess is as good as mine, currently waiting two days for a reply to my "I just get an error when I try to claim my membership DBC" ticket.
It depends on the category of your issue, cause its different people dealing with different stuff and they could be more or less busy. But generally, I'd say anywhere between a couple hours and a couple days. But more often than not, I'd say you usually get a reply in less than 24 hours.
Depending on the issue, I've waited 2-3 days, or received same day closure. Probably just depends on the workload tbh.