By default the administrator password does not expire. This can be changed by running a CLI session (Putty or your favourite SSH client) and running
/usr/lib/vmware-vmafd/bin/dir-cli user modify --account administrator --password-expires
Other accounts can be set to not expire using
/usr/lib/vmware-vmafd/bin/dir-cli user modify --account <account> --password-never-expires
More generally the syntax is
dir-cli | user modify --account <account name> |
| [ --password-never-expires | ] |
| [ --password-expires | ] |
| [ --login | <admin user id> | ] |
| [ --password <password> | ] |