Says something that we had to fight very hard indeed to get some restrictions into our CLAs, so that standby duties can not exceed 16 hours (was 24 hours before) and that the total of standby duty and following flight duty can not exceed 22 hours. However there is still a loophole that allows up to 31 hours in some very rare cases. Has never happened, but it will one day as long as that loophole exists.