To prevent Oracle from expiring your accounts a few short months after installation you can turn off the auto expiring feature.  When there’s no need for super security the auto expiry is a major annoyance!

ALTER PROFILE “DEFAULT” LIMIT PASSWORD_LIFE_TIME UNLIMITED;
ALTER PROFILE “DEFAULT” LIMIT PASSWORD_VERIFY_FUNCTION NULL;
ALTER profile “DEFAULT” limit FAILED_LOGIN_ATTEMPTS UNLIMITED PASSWORD_LIFE_TIME UNLIMITED;
alter user <USERNAME> identified by <PASSWORD>;
alter user <USERNAME> account unlock;