You can not simply invest your money at "compound interest" for an arbitrary number of years. Market interest rates change over time. And even if you would mana

You can not simply invest your money at "compound interest" for an arbitrary number of years. Market interest rates change over time. And even if you would manage to get some institution to guarantee you interest x for n years, that institution might go bankrupt before you get your money back. Some long running investments exist, like governments still paying off debts from World War 1. But you can not count on such deals being available when you need them. I think Andreas Eschbach handled it pretty well in his excellent novel One Trillion Dollars. It also has the premise of a heritage that compounds for a very long time. But it explains that there was a family whose sole purpose was to manage the fund for centuries until the heir was ready. (The book is not so much abut the wonders of compound interest as about the value of money).