4 ms·Doubling an investment is not too hard over 20 years.by pkaye 9y agoDoubling an investment is not too hard over 20 years.bdcravens 9y agoExcept he sold his Yahoo stock pretty early so he then had to make decisions on how to invest and grow the cash.pkaye 9y agoHe just needs to get 4% yield per year to double it in 20 years.