Potty train. Pull all-nighters. Work. Pay taxes. Retire. Play golf. Die.

Such is the natural order of things in life (with a few substitutions allowed here and there). But changes are afoot. Call it evolution or sheer boredom. Whatever the reason, more people say they plan to continue to work long past the traditional age of retirement.

Nearly half of 55- to 75-year-old workers plan to work during at least part of their retirement, according to MFS Investment Management. A whopping one-third plan to work throughout their golden years. Just 16% of those surveyed say they plan to retire and never work again.

According to a 2002 Gallup Organization poll, 83% of 1,000 nonretired American investors plan to work in retirement. Sixty-seven percent of those polled plan to continue working -- not for money, but for fun.

Why? Let us count the ways.

Would you like fries with that?
Let's start with the obvious: Money.

Let's face it, if you haven't saved enough, by the time you reach retirement age your options are limited. A word to the young whippersnappers out there reading this: Don't get cocky. Statistically, if you're a typical 40-year-old working American, there's a 50% chance your savings and investments total less than $25,000. That, my friend, is not nearly enough for your retirement. (Heck, $1 million may not even be enough.)

Your options:

Peace of mind is another biggie: Perhaps you have saved adequately, but are uneasy about the ability of your money to last as long as you do. The longer you keep money coming in, the less of it you have to crack out of your nest egg. Plus, in many cases, you can postpone taking Social Security or other benefits, which may result in a higher benefit when you do start collecting.

Boredom: Sure, many retirees plan to take time off and see the world. But at some point, they'll have to come home ... and then what? Plain and simple, many retirees have had trouble finding fulfilling ways to take up all the extra time.

Of all the reasons to continue working, if I were you I'd gun for that last one.

Dayana Yochim already did a stint in fast-food retail. She's hoping that she won't need to hone her sandwich-making skills to make it through retirement. The Fool's disclosure policy -- although already a well-balanced meal -- would actually like fries with its meal.