Long-term buy and hold only works if you can predict a long-term bull market -- or so says, Bernie Schaeffer, chairman and founder of Schaeffer's Investment Research.

Since stocks of all walks have been torpedoed in the wake of the financial crisis, pundits are calling into question the viability of the decades-old strategy. Long gone may be the times our grandparents and parents were able to invest in stocks for 10 years plus without rebalancing or cleaning their portfolios.

As part of The Motley Fool's series that seeks to answer the question, "Is long-term buy and hold dead?" Mr. Schaeffer weighed in. What follows is an edited transcript of our interview.

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

Bernie Schaeffer : I don't see it as a viable strategy, unless you have a way of predicting long-term bull markets.

In March 2000, the S&P peaked at more than 15 times its August 1982 lows. On the other hand, anyone who invested in the S&P from the middle of 1997 to date is very likely losing money. So if you believe we're about to embark upon a 1982-to-2000 run, "buy and hold" will work. In a much more challenging environment, such as the one we've experienced over the past dozen years, it will not work.

The lesson here is never to confuse genius with a bull market, and that powerful bull markets make almost any strategy that involves buying stocks look "smart." What's "dead" is the immutable belief that dominated the investment world as recently as a few years ago -- that buying stocks for the "long term" is always a good deal and the idea that a 100% portfolio exposure to stocks makes good sense.

Schonberger : Do major gyrations in stalwart stocks like General Electric (NYSE: GE) call into question the strategy? Are the days of the blue chip over?

Schaeffer : Let's not forget that GE turned out to be a case of financial engineering in blue-chip clothing. There's also the recent transformation of American International Group (NYSE: AIG) and General Motors -- two stalwarts of the Dow Jones Industrial Average of 30 "blue chip" stocks [that turned] into penny stocks. Before that, there was Fannie Mae (NYSE: FNM) and Freddie Mac (NYSE: FRE) and before that, WorldCom and Enron.

I think the days that a company can remain dominant in the markets for decades at a time are over. Life simply moves too fast these days. There are no "permanent blue chips." Even Wal-Mart (NYSE: WMT), while still dominant in retailing, has been dead money for stock investors for a decade.

Schonberger : What do you say to investors who have implemented the long-term buy and hold strategy for years and have seen their holdings simply evaporate in the wake of the market meltdown? And it could be years before any of it comes back...

Schaeffer : Always keep a significant portion of your holdings in cash or in bonds -- at least 30%. Stocks are risky investments, even over the "long term." Investors should never be 100% invested in the stock market. ... Asset allocation is critical. There should always be a mixture of stocks, Treasury bonds, and cash.

Schonberger : What about diversification?

Schaeffer : Diversification is overrated and gives investors a false sense of security. In bad times, stocks all move down together and in good times you don't need to be very diversified. One of the biggest jokes on investors over the years has been "diversifying" into many stock mutual funds only to find these funds basically own the same stocks. Continued...