As you know the tickets are only valid between a somewhat short amount, typically between 12 and 24 hours, however the keytab is valid as long as you find it valid.

How long is a Kerberos ticket valid?

By default, all Kerberos Tickets have a 10 hour lifetime before they expire, and a maximum renewal period of 1 week. If you want to renew your ticket, you must do so before it expires. If you wait until after the 10 hours is up, then it is too late, and you must get a new one.

How do I know if my Kerberos ticket is expired?

To confirm that the ticket is expired, run the klist command. This command checks for a credentials cache. If no credentials are cached, then the ticket is expired.