Firstly it depends whether the agent is IATA accredited or not as without IATA accreditation they get the tickets issued by a third party (called a consolidator) which will normally only happen during weekdays. Then, as a general rule it will depend on the type of ticket and where the booking was made (online or in an agency/over the phone). For simple tickets on major carriers (e.g. QF domestic or trans-tasman), many agents would robotically ticket from their website or agency. For complex international or for deeply discounted tickets it's more likely that manual intervention will be required which may need specialist help (only available normal weekday business hours) or could take a little time. Unfortunately there's no quick answer.