But don't ease up on investing today with the idea that you can fill the gap by working more later. You may not be able to find or keep a good job.

Retirement surveys suggest that most of us stop working earlier than we expect. That might change as the growth of the labor force slows, which could spur companies to recruit older workers.

Then again, employers might just offshore even more work than they do now. If you think of your career as a part of your portfolio - call it your labor capital - then assuming that you can squeeze out another two years of earnings is akin to deciding to get 10 percent a year on stocks. It'd be nice, but it's not entirely up to you.