When Outlook 2007 and 2010 subscribe to an internet calendar (via a webcal:// link to an iCalendar or vCalendar file), how often do they auto-update? Is there a way to configure this, either in the file downloaded or in Outlook preferences? I know the file can specify a minimum refresh interval (via the X-PUBLISHED-TTL field), but I don't see a way to explicitly specify a recommended interval.
Outlook relies on the custom property X-PUBLISHED-TTL to set the download frequency but unless set in the file you subscribe to, there is no way to force within outlook an update frequency (nor in google calendar).