Sadly the radio hosts weren't too wrong. The average lifespan of a goldfish or a koi in the USA is about 3 weeks - ask any vendor of these fish. Now an observed average captive lifespan and a reasonably possible natural lifespan are apples and oranges, of course. In Japan, prized koi live up to century and are passed on from generation to generation. I don't think goldfish would be far behind. IIRC, 50 years is mentioned when living in temperate climates.