What would you do if your financial planner prescribed the following advice? Save and invest diligently for 30 years, then cross your fingers and pray your investments will double over the last decade before you retire.

You might as well go to Las Vegas.

Yet that’s exactly what many professionals and fancy financial calculators have been telling consumers for years, argues Michael Kitces, director of research at the Pinnacle Advisory Group in Columbia, Md., who recently illustrated this notion in his blog, Nerd’s Eye View.

The advice is never delivered in those exact words, of course. Instead, this is the more familiar refrain: save a healthy slice of your salary from the start of your career, invest it in a diversified portfolio and then you should be able to retire with relative ease.

The problem is that even if you do everything right and save at a respectable rate, you’re still relying on the market to push you to the finish line in the last decade before retirement. Why? Reaching your goal is highly dependent on the power of compounding  or the snowball effect, where your pile of money grows at a faster clip as more interest (or investment growth) grows on top of more interest. In fact, you’re actually counting on your savings, in real dollars and cents, to double during that home stretch.