With construction companies continuing to report record-setting numbers, it's time once again to scratch our heads and wonder: Just how long can this global energy, commodities, and construction boom go on? Companies like McDermott International (NYSE:MDR), Foster Wheeler (NYSE:FWLT), Fluor (NYSE:FLR), Jacobs Engineering (NYSE:JEC), and URS (NYSE:URS) have been riding this wave for a while now, and their shareholders have plenty to show for it.

So is it time to get out, or is the party just getting started? A few things to consider: construction is cyclical, so after the boom comes the bust. On the other hand, this boom is global and pretty much unprecedented. However, China's stock market may now be in a bubble, and if it pops, the party might be over for a while. And, of course, let's not forget skittish U.S. consumers So, as they used to say in the NFL, "You make the call."

For Fluor and its peers, the call might be less complicated. As some of the most diversified engineering and construction firms in the world, they all have more than one board on this wave. So they can hop from refinery construction in Asia to coal-fired power plants in the U.S. to embassy construction in the United Arab Emirates, and so on.

Last year for Fluor, oil and gas was the big winner. This year, it's oil and gas and a re-energized power plant business. Just how big a boom are we talking about here? In this latest quarter, Fluor's net income jumped 243% to $93.7 million, mostly because operating profits in the company's biggest segment, oil and gas, leapt 28% to $112 million. Likewise, there was a tripling of operating income in the power plant business, which rose to $6 million.

I'm inclined to think this global boom might take a breather soon. The U.S. economy is slowing down, and the rest of the world might not be as "decoupled" from it as we've been told.

Besides, even if the boom continues, this is probably not the time to be buying construction firms. As one Fool has pointed out, the best time is when they're flat on their back. So, especially for those in this group trading with plus-sized valuations, including Fluor, it's probably wise to pass for now.

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Fool contributor Ron Vlieger doesn't own shares in any of the companies mentioned, but does welcome your questions or comments. The Motley Fool has a disclosure policy.