In 30 years of freshwater tanks, and 5 years with a reef, I have left tanks unattended for 2 weeks at least once or twice every year. Key is to have backup equipment (tried and tested) that can be put in place, on a separate power circuit, to back up all essential systems. Vortech pumps with battery backups. Auto feeders. Think thorough what can go wrong and make sure that there a back up system to deal with it. No disasters yet...