Anything up to a week will the fish won't require feedings, I just perform a large water change and basic maintenance on the filters, and have someone check daily for issues with leaks or power outages that could occur. Anything over a week will require some intervention, best to train a family member or friend prior to leaving. Then pre-measure the food for each feeding with a little lighter than normal amount. So when someone comes to check the tanks each day have them feed every other day if it's over a week.