Set Values for Ticket-Granting Tickets
You must specify the default values of all ticket-granting tickets for new principal profiles on the Realm Defaults tab. Changing the default value doesn't affect the ticket values for existing principal profiles.
The KDC (Key Distribution Center) ultimately determines the lifetime of a Kerberos ticket. The KDC can be configured to allow ticket lifetimes within a certain range, and overrides your request if it falls outside of the allowed range. (To get a TGT, you must authenticate to the host.)
Note: You can modify the settings for a current ticket in the Authenticate dialog box when you obtain a new ticket.
To set the default values for all tickets issued for a realm