The U.S. equity market remains in a secular bull market, but after five and a half years it is entering a mature stage and investors can expect more price swings, according to Liz Ann Sonders, chief investment strategist of Charles Schwab & Co. Addressing about 2,000 advisors at Schwab's annual Impact conference, Sonders quoted the late Sir John Templeton to identify the stage of the current bull market in stocks.

Bull markets are born out of pessimism, grow on skepticism, mature on optimism and end in euphoria, she paraphrased Templeton. The U.S. today finds itself in the third stage, enjoying stable economic growth, an environment in which equities can continue to outperform as the bull market approaches maturity.

But the rest of the world is still afflicted with a divergent set of problems. The Eurozone and Japan continue to wrestle with deflation, while emerging markets are forced to address inflation.

That's one reason why "volatility is with us to stay," she said. Viewed on a historical basis, the U.S. is one year away from the end of this bull market and two years away from the next recession, though she indicated both cycles might well outlast the historical averages.

Sonders noted that in its latest GDP reforecast, the IMF upped its GDP forecast for the U.S. while reducing it for Europe. She quickly added the IMF's record was spotty at best.

Even if the U.S. is the cleanest shirt in a dirty laundry basket, Sonders doesn't expect the American consumer to provide "much oomph" for the domestic economy. That despite the fact that consumer spending is down from 72 percent of GDP before the recession to 67.9 percent in the most recent reading.

The anemic growth of government spending in recent years has been a drag on economic growth, but she expects it to normalize in the next year. In contrast, the private sector has been expanding at a rate in line with typical recoveries. "The divergence between the private sector and overall economic growth will narrow," she said.

The next phase of this recovery should be driven by business capital spending. This time the cycle could "elongate the recovery."

Since 1980, the shape of recoveries has changed from the sharp bursts witnessed in the post-World War II era, when the U.S. economy was more dependent on heavy industry and less exposed to an array of service sectors. In recent decades, "recoveries have been slow and prone to mid-cycle slowdowns," she said. "In this recovery, we've had one [a mid-cycle slowdown] every year."