For decades, experts have told investors that they should invest more conservatively as they grow older. But if you have visions of wealth that will last for generations to come, getting sheepish about risky investments could be the worst move to make.

Going beyond your needs
In analyzing your financial situation, it's easy to focus solely on your own individual needs. While you may have important outside goals for your money -- such as providing for children and grandchildren, or making a sizable bequest to a favored charity -- you'll typically put them on the back burner until you ensure that you've provided for your own self-preservation.

Obviously, setting priorities in that order often makes the most sense. Many seniors don't have enough resources to meet their own needs while still fulfilling their wishes to help others. And with unrelated third parties or even family members sometimes seeking to take advantage of an elderly person's wealth, you have to put yourself first just to protect yourself.

But clearly, if you have both the means and the desire to help others, rather than just spending your money on yourself, you shouldn't just invest with yourself in mind. Instead, consider not only your own time horizon, but also how long your money will stay invested before it's used for the purposes you intend for it -- even that timespan extends beyond your lifetime.

Keeping it in the family
An example can help clarify how your investments might change to suit your particular situation. Consider an 80-year-old retiree with $10 million in assets, whose primary expense is skilled nursing care, which I'll assume costs her $150,000 in annual out-of-pocket expenses.

Obviously, if you only look at this person's own financial situation in isolation, you'd conclude that she is absolutely secure. Even with interest rates at ridiculously low levels, a mix of insured bank CDs and high-quality bonds would suffice to provide ample income to cover her expenses, with plenty to spare. And with a nest egg that could pay those expenses for 60 years without any income at all, she has enough protection against inflation to cover her for the rest of her life.

However, if our retiree also has a large family of children and grandchildren for whom she'd like to provide, that changes matter greatly. While her personal time horizon may only be 10-20 years, her grandchildren have needs that could last for decades beyond her lifetime.

In that case, keeping her money invested conservatively for 20 years could easily cost her family millions in lost growth. Consider the impact of missing out on some fairly aggressive investments since 1989 -- even including the declines over the past year and a half:

Stock

20-Year Annual Return

Lost Appreciation On $100,000 Investment

Nike (NYSE:NKE)

19.1%

$3,119,000

Best Buy (NYSE:BBY)

27.7%

$13,086,000

Colgate-Palmolive (NYSE:CL)

15.9%

$1,723,000

Hewlett-Packard (NYSE:HPQ)

11.3%

$645,000

Home Depot (NYSE:HD)

17.4%

$2,273,000

American Express (NYSE:AXP)

6.6%

$159,000

PepsiCo (NYSE:PEP)

12.4%

$829,000

Source: Yahoo! Finance.

Obviously, not all stocks have historically done this well. But over a long period like 20 years, most stocks have risen in value most of the time. Staying out of them completely in favor of conservative investments would have cost your family a lot of lost wealth.

Why not get it?
Of course, some would say that people in this position don't really need that extra money. They certainly don't need to put it at risk in the market; they can live quite easily on simple interest.

But on the flip side, there's no reason not to put it at risk. Even in a worst-case scenario, in which they lost everything they put in stocks, they'd still have plenty to live on. Meanwhile, it's much more likely that the good those greater returns might do their families could make a huge difference.

So when you're considering your own investment strategy, think about all of your financial goals -- not just the ones that involve you directly. If others are important to you, spend at least a little time to consider what investments would be best for them. Then, if you can get your own finances squared away, do what you can to help them.

More on investing for the long haul:

You can learn more about estate planning and other ideas to keep your money in the family by reading our Rule Your Retirement newsletter. A free 30-day trial opens the door to a wealth of great information.

Frustrated with your 401(k)? Even if your employer's plan isn't the greatest, you don't have to give up your dreams of a happy retirement. Get the tips you need to turn your retirement savings around in our special report, "How to Make the Most of Your 401(k)" -- just click here for instant free access.

Fool contributor Dan Caplinger invests partially for his 4-year-old daughter. He doesn't own shares of the companies mentioned. Best Buy is a Motley Fool Stock Advisor selection. American Express, Best Buy, and Home Depot are Motley Fool Inside Value selections. PepsiCo is a Motley Fool Income Investor recommendation. The Fool owns shares of American Express and Best Buy. Try any of our Foolish newsletters today, free for 30 days. The Fool's disclosure policy is our legacy to you.