Remember Kerberos tickets after reboot
By default, the kerberos ticket cache is placed under /tmp, which is cleared out on reboot.  You can specify your own location for the ticket cache, in a location safer for long term storage, by passing the "-c" flag to kinit, and setting KRB5CCNAME to point to the same location, so ssh will use it.

$ kinit -c ~username/mykrbcache
$ export KRB5CCNAME=~username/mykrbcache
$ ssh kerberoshost
...
$ reboot
...
$ export KRB5CCNAME=~username/mykrbcache
$ ssh kerberoshost
...