Another thing not considered is how much harder it becomes to maintain the return at higher bases, while diversifying so that there are no major drawdowns. And on the topic of drawdowns, I think this is the biggest flaw in compound interest mythology - a minor drawdown (permanent loss of some capital) in the early years causes disproportionately large effects on the end result. Best to run a Monte Carlo simulation using some assumptions for inflation, range of returns, etc. There are various websites that do this for you.