Usually if you keep them in an aquarium and not a bowl and treat them like any other tropical fish, meaning have plenty of filtration, air movement and change 1/2 the water monthly, but keep the water temperature lower, they will live for many years.

When I was a kid my grandmother used to keep a goldfish bowl for me. During the week when I wasn't there she would put them in a glass and wash the bowl out with soap and wonder why they would be dead when I came to visit on the weekends.