Minor tickets take about 2-5 days from my eperience. Some that requires some bigger checking may take longer.
Exception may be the ones from
premium service (like rune transfer) that have a specific time of completion.
However, Help Desk its not a way to hurry up a ticket. Its a tool that helps you get answers to questions and sollutions to problems concerning the game. There are also some exception about what type of issues that HelpDesk cant solve.
More about the HelpDesk
here.