Good news for investors rattled by the "bear market" in many stock indices is that the selling may only last a few months --the bad news is that another big lurch lower is likely and that previous peaks will not be revisited for years. Worries over China, collapsing oil prices and rising U.S. interest rates have pushed many European stock markets down more than 20 percent from highs hit last year, signifying losses of trillions of dollars for investors.