NEW YORK (CNN/MONEY) - The price of crude oil has risen steadily for a year and continued to surge in the past month, climbing as high as $55 a barrel.

But the real oil shock could be a pleasant one -- a surprise drop in prices sometime before next spring.

Traders and some analysts expect the price of oil to run up to $60 or even $70 a barrel in the next month or two. That may well happen. Momentum is intense, and it's notoriously hard to pick the top for a commodity in the midst of a runup.

But some of the smartest observers think that though prices could move higher in the very near term, an oil price above $50 a barrel is ultimately unsustainable.

The reasons for the past year's runup all have to do with transient factors. The war in Iraq not only destroyed some oil wells, but also raised fears of more damage to production facilities. Most analysts figure that the price of oil now includes a so-called terror premium that ranges from $9 to $15.

But that's not all. Strong worldwide growth, particularly in China, has contributed to global demand. In addition, hurricanes in the Gulf of Mexico temporarily disrupted both local production and, even more important, refining.

With some refinery capacity sidelined, supplies of distilled products, such as gasoline, diesel fuel and heating oil have declined even though inventories of crude oil actually rose in the most recent week. Demand for distillates is running 4 percent above year-ago levels. And analysts point out that oil prices rarely top out before mid-winter, because of the jump in demand for heating oil in November and December.

The picture looks entirely different, however, if you look out beyond the current squeeze.

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There are always risks in the oil business, given the political volatility of many of the countries involved. But current production is adequate to cover current demand.

More important, production is expected to rise substantially both this year and next. In addition, there are signs that the Chinese economy may be starting to slow.

Once the supply/demand balance begins to tip the other way -- which could happen within four or five months -- oil prices could start to slide. And some analysts believe that they could fall as low as $35.

What, in practical terms, does this all mean for investors?

For starters, it makes sense to wait a few months to add any oil stocks to your portfolio. Shares of energy companies haven't fully kept up with the increase in crude oil prices, but if oil falls the stocks will probably sell off to some extent.

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But there's a much more important issue, which could affect the stock market as a whole. The rise in the cost of imported oil has reduced overall U.S economic growth by as much as three-quarters of a percentage point, according to recent comments by Federal Reserve chairman Alan Greenspan.

If the oil price does ease by next spring, the reverse would be true -- the economy would get an unexpected shot in the arm. Moreover, that incremental growth would be non-inflationary.

Current share prices are running well below the norm for a recovery. If oil prices ease and growth improves, stock prices should enjoy a lift of as much as 20 percent. Sometimes surprises turn out to be nice.

Michael Sivy is an editor-at-large for MONEY magazine.