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 to hold.

You buy with the aim of 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 sevenfold 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 If we no longer have great faith in the company's promise, if the reasons we bought are no longer valid, if we simply find much more compelling investments -- these are all rational causes for selling.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 bonds over periods of 20 years or more.

And although you can never expect to 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 know when a stock is overvalued.

Think of Oracle (NASDAQ:ORCL), which has averaged a 20% gain over the past 20 years, or ExxonMobil (NYSE:XOM), which has averaged 13%. Sure, if you knew when either was going to underperform for a year or two, you could have gotten in and out of the stock accordingly and earned much more. But we never really know how a stock will perform in the short run.

Moreover, stocks don't always move in relation to their value. A stock may be overvalued but keep rising, or undervalued and still fall more. If you're pretty sure a stock has gotten way ahead of itself, selling some or all of your position and moving the money into a more compelling value proposition can be smart. But if you have long-term faith in the company as a healthy grower, you might do best just to hang on while keeping tabs on it to make sure you still want to hold your stock.

So go ahead and buy to hold. This is a particularly promising time to buy stocks, as so many are on sale right now. Whether you buy broad-market index funds, carefully chosen stocks, or a combination, thinking long-term with your investments is the smart move.

Hard times create great opportunities for those who can take advantage of them. Read why Jim Mueller thinks now's the time to grab stocks like candy in a candy store.

Longtime Fool contributor Selena Maranjian owns shares of Berkshire Hathaway, McDonald's, and Coca-Cola. Berkshire Hathaway and Disney are Motley Fool Stock Advisor selections. Berkshire Hathaway, Disney, and Coca-Cola are Motley Fool Inside Value picks. Coca-Cola is a Motley Fool Income Investor selection. The Fool owns shares of Berkshire Hathaway and Oracle. Try any of our investing newsletters free for 30 days. The Motley Fool is Fools writing for Fools.