I've had the same 4 goldfish for several years, but my oldest is a fancy fantail who is at least 11 years old. He was in a pet store and looked horrible, I told the manager I'd give him a dollar for him and he was mine! I nursed him back to health and he flourished. He has lived in two states and dwelled in both tank and pond. He might be blind, but he seems to still be a feisty one.
My second oldest is a regular comet goldfish I won from a little county fair. He would be at least 6 years old.