When the market is on a tear, it's tempting to sit back and wait for a pullback. But smart investors know that the best strategy isn't timing the market -- it's time in the market.The market hitting new highs actually isn't uncommon. In fact, a J.P. Morgan study found that since 1950, the S&P 500 hit a new high on about 7% of its trading days. Meanwhile, on nearly a third of the days it hit a new high, it never traded below that price again. That's why dollar-cost averaging is so important. And one of the b ...