These fields are used as durability reminders and can be accessed from the Charges menu then Options:
1st durability assessment reminder after 13 weeks of case closure.
2nd durability assessment reminder after 26 weeks of case closure. (Please note the number of week’s reminders is determined by the service contract).
Having the check box marked with zero weeks means the service contract has case durability fields enabled but no reminder is set.
Note: Durability Reminders can be defined globally for all cases in the Options > Admin Management Console > System Reminders tab.