The lights have easily been off for more than 12 hours for the last week, and 10 or more everyday since I have had them.
I don't know the age of my goldfish. At the beginning of this month I bought each for $4 from a couple who had the goldfish in a pond and were wintering their goldfish in a tank. Last year they heated the pond, and it had cost them too much. So they had decided to use their tank.
My biggest one is 5" not including the rear fin. Maybe they are pretty old, but they're really very pretty when they are happy.