You mis-characterize what Buffet said. He said the results over the next 100 years would justify the purchase price, not that the payback period is 100 years.
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I've never seen Buffet make any predictions. However, he has been declared wrong, senile, and insignificant many times. Most recently at the time of the dot-com boom. Last time I looked, Buffet was still on top and hasen't been replaced by anyone who has written him off. He's in a league of his own and doesn't need the approval on minor leaguers.
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Another Buffett Prediction, Japan Edition [View article]