Buy and hold. It's a familiar investing maxim, and one frequently under attack these days. It still has its supporters, though, as many believe you can find stocks you'll probably never want to sell. Long-term investing can also play an important role in helping your portfolio recover.  

I'm a practitioner of buying and holding, myself, but I'd like to make a little clarification. Here in Fooldom, when we talk about buying and holding, we don't mean to suggest that you should never sell or that you should buy and then never look at the stock again. Instead, think of the strategy as buying tohold.

You buy with the aimof holding for a very long time. That is, after all, how many of the world's best investors made a lot of their money. Berkshire Hathaway 's (NYSE: BRK-B) Warren Buffett, for example, has seen his very long-term investment in Coca-Cola (NYSE: KO) increase around seven-fold since 1988, and his investment in The Washington Post Co. (NYSE: WPO) has surged more than 60-fold since the 1970s.

But along the way, Buffett sold shares of McDonald's (NYSE: MCD) and Disney (NYSE: DIS). Investors such as Buffett -- and us -- shouldn't always hold forever. If we no longer have great faith in the company's promise, if the reasons we bought are no longer valid, if we simply find much more compelling investments -- these are all rational causes for selling.

Responding to naysayers
Not everyone thinks that buying and holding is a smart move. They have a number of reasonable arguments why you can't count on gains as a long-term investor. (Check out a lively give-and-take among Fools, starting with our June article " So Is Buy and Hold Dead or What?")

For instance, some will argue that while the market may have averaged annual 10% gains over the past 70 or 100 years, it may well perform very differently over the 20 or 30 years that you invest. They argue that stocks don't always beat bonds. Well, true. But professor Jeremy Siegel has shown that stocks have nearly always topped bondsover periods of 20 years or more.

And although you can never expectto earn a 10% average, it's a reasonable starting point for your planning. But feel free to go ahead and expect less and save and invest more; if you end up earning 10%, you'll just be better off.

Still, some point to the fact that stocks have gone nowhere over the past decade. But hold on there -- that's just for those who bought at the top of the market in 1999. Remember that most of us keep adding money to the market as we're able. So while your 1999 investment in the S&P 500 is in the red, your 1996 investment is up more than 50%. Those who invested a year ago are up about 14%. Each year's investment will offer a different return, and over decades, you're likely to do well overall, if you keep adding money into the market.

Other naysayers will argue that if you buy and hold through thick and thin, you'll sometimes be holding onto stocks when they're significantly overvalued. True enough. But many of us are not expert stock analysts. We don't always knowwhen a stock is overvalued. Continued...