Man investors still cling to a buy-and-hold mentality as a backlash against the day-trading debacle of the New Economy days in the late 1990s, that strategy has been alarmingly ineffective in the past five years.  Now the market experts are wondering if the market is on the cusp of another important shift.  During the past five years, more institutional investors have been employing timing models and sector-rotation strategies to benefit from the short-term upswings in the market, as well as raising their investments in hedge funds, according to market sources.  Buy-and-hold has an old-school charm, a conservative voice that sounds wise when speaking of patience.  But that’s because so many people making their living in finance today came of age professionally in the 1980s and 1990s, says James Paulsen, chief investment strategist at Wells Capital Management, an investment advisor that caters to institutional investors.   The buy-and-hold method works well in a bull market because the entire market has a general upward trend, so a portfolio manager does not have be particularly good at stock picking to post positive results, Paulsen says.  The market was in a bull run from 1982 to 2000, proving all those buy-and-holders right but with the future looking so uncertain a new spin on this old strategy might be called for in my own personal finance.