I like to emphasize success is more predicated on savings rate than the returns of your investments.
A person saving 5% will have to work 19 years to accumulate 1 year of expenses.
A person saving 6% will have to work 16 years to accumulate 1 year of expenses
A person saving 10% will have to work 9 years to accumulate 1 year of expenses
A person saving 15% will have to work 6 years to accumulate 1 year of expenses
A person saving 20% will have to work 4 years to accumulate 1 year of expenses
A person saving 25% will have to work 3 years to accumulate 1 year of expenses
A person saving 33% will have to work 2 years to accumulate 1 year of expenses
a person saving 50% can work 1 year and save 1 year of expenses at same time.
You could use that same math then figure out if you work 25 years and save 50% then you have 25X expenses of when you started... if you can pay off mortgage by 25th year (and therefore cut expenses) retirement can be predicted better than if you saved 6%, received a 4% match and spent 94% of what you earned. The #1 factor every investor has to their own success is their savings rate. As individual investors we have little control over performance, and even if we change our risk profile, we still have less control over our returns than we probably want.