After Free Busy synchronization was implemented and FB data has been synchronized, it can be seen only going back for 2 or 3 months. Why does this happen? Did FB agent synchronize the FB information incompletely?
FB agent cannot synchronize the FB information partially. FB information for a user is stored inside a so called "message" file (this behavior was changed in Exchange 2007 and FB can be stored inside the mailbox), and FB agent does synchronize the entire message.
The mentioned above issue with the FB information not being visible only for a specific period of time is environment related and could be caused by Outlook settings. By default FB information is being published for 2 months.
For more details please see the attached screenshot which shows the setting in Outlook 2007.