Hard to remember exactly but his GrandFather and Father both maxed out around 20 inches and lived about 14 years....I think two factors to consider are better quality food/filtration available now and I am a better fish keeper then I was....
Will be interesting to see how long this old boy lives for then. There must be a hell of an attachment to a fish like that when you've had it for that long, it would nearly be like losing a dog!