I don't think you have to be an engineer to realize that you don't want to build a permanent structure on swampland or sand if you don't have to. But a momentary structure that just needs to fulfill its purpose for a short period of time? That's another story, and it may be the case with ShawGroup (NYSE:SGR) as well.

First, the financials. While revenue rose more than 66% in Shaw's reported second-quarter results, earnings per share still came in under the average estimate. Now, some of that underperformance was due to a write-off, which I think you can argue should be added back, but I don't think investors are going to be so willing to forgive the $0.10-or-so impact from higher costs in certain project contracts.

But that's not to say that it was a terrible quarter. The backlog rose about 10% sequentially, with almost half of the $7.6 billion expected to be realized in the next year or so. And if you've been following this story, the makeup of that backlog won't shock you -- lots of new power projects (including a fair bit of nuclear), and quite a bit of work related to the chemical industry as well.

The bigger issue in my mind is how long this can all last. Sure, the Dukes (NYSE:DUK) and Dominions (NYSE:D) of the world are in the market for new plants and environmental equipment, but those tend to last for quite a long time. Likewise for the DuPonts (NYSE:DD) and Dows (NYSE:DOW) of the world -- chemical companies may be investing in plants today, but that often marks the upper end of the cycle.

What's more, Shaw has never really been what you'd call a champion in terms of return on invested capital. In other words, over the long haul, this is a company that really hasn't done all that much with the money that lenders and shareholders have given it.

All that said, not every stock in your portfolio has to be a long-term champion. I've held some stocks for 10 years and other stocks for 10 months, and I can tell you that the cash profits from one spend exactly the same as the other. And I'm not quite sure about the point at which I'd pull a shroud over the large-scale construction/engineering sector -- there are still a lot of projects yet to be booked into backlogs and plenty of profits yet to be realized.

Still, that poor historical return on capital means that you need to be careful and nimble. There's nothing wrong with making hay while the sun shines, but don't get suckered into a long-term relationship.

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Fool contributor Stephen Simpson has no financial interest in any stocks mentioned (that means he's neither long nor short the shares).