CNBC's Jim Cramer recently proclaimed, "You haven't made any money in 10 years, so buy and hold must come into question." Another member of the CNBC family, Fast Money's Jeff Macke, stirred the pot further when he declared 2008 to be the year that long-term buy and hold died.

They're among a small camp challenging whether buying and holding even the bluest of blue-chip stocks, such as IBM (NYSE:IBM) or Coca-Cola (NYSE:KO), over the long-term is still a viable strategy.

In an effort to answer the question, "Is long-term buy and hold dead?" the Fool has set out to interview financial experts for their insights and opinions.

Jim Oberweis continues to believe in the viability of buy-and-hold investing. Oberweis is president and lead portfolio manager of Oberweis Asset Management. He is also president of The Oberweis Funds, a collection of funds focused on emerging growth companies (current investments include Neutral Tandem (NASDAQ:TNDM), Green Mountain Coffee Roasters (NASDAQ:GMCR)) and emerging markets.

What follows is an edited transcript:

Jennifer Schonberger: Do you think long-term buy and hold is dead?

Jim Oberweis: Let's think about why and how the strategy evolved. Over a short period of time, it's extraordinarily difficult -- intrinsically impossible -- to guess the direction of the market consistently. At the same time, we know that over long periods of time, the market has a propensity to go up in value.

When you go through periods of volatility, it's certainly easy to challenge whether that's the right plan. I've never said markets won't go down -- invariably they will go down, but they often will go up over long periods of time.

There are a few periods as long as 20 years where the market didn't go up as much as bonds. Those are rare periods, and the market produced positive returns in those periods.

So, you can't tell what the market is going to do in a short period of time, but you know that the market goes up over long periods of time. The logical solution would be to stay fully invested in the market for long periods of time.

Schonberger: What do you say to people like Jeff Macke and Jim Cramer, who say that the thesis is dead?

Oberweis: Show me some quantitative evidence that someone's right, and then I'm interested. I'm a numbers guy. I don't know anyone who has been able to time short-term fluctuations in the market over long periods of time and make a lot of money doing so. That's why I think [buy and hold] is still an effective way to play it for most people.

Though, one caveat to what I'm saying is that I do think that in extreme periods there may be opportunities to add value by reducing or increasing equity exposure. For example, if you looked at technology stock valuations in 1999, they were far above median market valuations. There could have been an opportunity there to reduce equity exposure and earn excess returns.

Based purely on math, valuations were two or three standard deviations above typical valuations for tech stocks. At the same time, if we looked at March of this year, valuations were two or three standard deviations below the mean. …

The risk/reward ratio goes up a lot if you're buying stocks when they are two standard deviations below mean valuations and you're selling stocks when they're two standard deviations above mean valuations.

Schonberger: In terms of the "long" in "buy long-term and hold," how long are we talking about here? Can you really hold the market forever, or should investors remain cognizant of valuations, getting out when stocks are fairly or overvalued?

Oberweis: You can buy and hold the market forever, but not individual stocks. The individual stocks that comprise the market are businesses, and just like any other business -- some will succeed, some will fail.

The best thing 95% of individual investors can do is set up an asset allocation of investment vehicles that have relatively low correlations to each other and keep that allocation constant -- with the exception that over a period of time it becomes more conservative as the individual ages. Usually that plan includes a consistent allocation to equities, which I think you would deem a buy-and-hold strategy. It's the classic financial plan.

Schonberger: Is buying the U.S. market viable for the long term, or should we be looking to emerging markets as the world's growth engine, therefore buying foreign stock such as China Mobile (NYSE:CHL) or China Petroleum & Chemical (NYSE:SNP)?

Oberweis: Both strategies are viable but with different risk profiles. For the foreseeable future, the U.S. will be one of the more stable places to invest. In places like China, companies will have stronger winds at their back in taking advantage of the urbanization of process. It's akin to the industrial revolution in the U.S.

China is undergoing more transformation, so I certainly think the returns in China will exceed the returns in the U.S. over the next 20 years. I think it makes sense to own both for portfolio diversification.

Schonberger: And diversification is important now more than ever, right?

Oberweis: Absolutely. The investment wisdom goes in fads. The reality is oftentimes the fad you read about in the press -- the fad that has happened in the most recent cycle of the market. For example, we're having this conversation because people lost a lot of money in the stock market over the past couple years. But that's normal. The stock market goes through cycles.

This is a nasty cycle, but it's not a different game. The rules haven't changed. If anything, the practices of investing for the long haul are more important now than ever. People run into trouble after a major correction by selling equities. When you have a major correction, that's the time to increase your exposure to equities because that's the opportunity to buy stocks at much lower-than-normal prices. Very few people have the intestinal fortitude and discipline to do that.

Schonberger: Many have compared the current market cycle to the 1970s. Will the next decade mirror the 1970s?

Oberweis: In some aspects. The opportunities in the 1970s stemmed from extraordinarily low valuations. Those valuations came crashing down due to risk aversion rising from 1973 to 1974. In 2007 and 2008 we saw some of those same things. In many of the companies in our portfolio we saw valuations come down not because the underlying business was in trouble, but because the multiple of earnings that people were willing to pay to buy shares in that company decreased.

We've seen P/E multiple contractions throughout the portfolio, but it tends to be a good time to buy stocks because you tend to get some reversion back to more normal valuations, and then the opposite effect occurs -- you get a P/E expansion in multiples, and the stock price will go up -- sometimes very quickly.

Schonberger: Is index investing still a viable strategy?

Oberweis: It depends on what you're seeking to index and how many people are participating. Indexing is an appropriate strategy for large-cap investing, but I would not advocate indexing for small-cap growth or international investing.

In the stock market, everyone is playing the same game. The amount of information available is similar for all of us. In large-cap markets, where there are lots of participants and lots of competition, I think indexing is very effective because it's hard to beat the mean. However, in areas like small-cap growth stocks or emerging market stocks, it's very different. For example, in our micro-cap investments, we may be one of three or four investors.

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Jennifer Schonberger does not own shares of any of the companies mentioned in this article. Coca-Cola is a Motley Fool Inside Value and Income Investor recommendation. Green Mountain Coffee is a Rule Breakers selection. The Motley Fool has a disclosure policy.