We have situations right now where you can be on standby from 03.00 local until 21.00 local with the distinct possibility of being called out to fly a multiple sector nearly 12 hour night duty starting near the end of the standby period. Given this duty often goes into discretion and if you get up at a normal time say 06.30 you could be up for well over 24 hours before you land. We certainly hope it will not happen but I had a co-pilot recently who had this scenario occur on the flight before.