If you need an update immediately, you don't have to wait for the automatic cycle. You can manually trigger a download: Administering the offline address book in Outlook
If an update is made just after the server finishes its 8-hour cycle and just before your Outlook client does its 24-hour check, you could wait nearly two full days for the change to appear automatically. How to Manually Force a Download how often does outlook download the offline address book
The "delay" you might experience when a new employee is added or an email changes is caused by two separate schedules: If you need an update immediately, you don't
: Outlook only checks for and downloads these updates once every 24 hours . If you need an update immediately