The default dirsync period between On-premise and Office 365 is 3 hours.
This for many people is too long
If you wanted to change the default sync period then firstly navigate to the Windows Azure Active Directory Sync directory on the member server where the Directory Sync tool is installed.
Older version the directory will be called Microsoft Online Directory Sync.
In this folder open up the file Microsoft.Online.DirSync.Scheduler.exe.config file.
Adjust the setting <add key=”SyncTimeInterval” value=”3:0:0″ />
For example if you wanted to bring this down to 5 minutes then change this line to the following. <add key=”SyncTimeInterval” value=”0:5:0″ />
Close and Save the file and then restart the Windows Azure Active Directory Sync Service
And here you go