This is definitely good "rule of thumb" advice to

This is definitely good "rule of thumb" advice to people investing in stocks, but there are some details that determine the scope of "life savings" that need consideration. Things to weigh are the actual cash value, how long would it take to replace if lost, and mainly, what impact would it have on your financial future if most or all of the investment were lost. In some cases the potential upside rewards far out weigh the impact of the potential downside spanking.