Work Smarter, or Work Longer?

I guess the longer working hours became more and more common only in the last decade or slightly more, but it’s quite surprising that it seems to be going strong even to this day in many companies.
And not only do companies demand more of the employee’s time, employees surprisingly take pride in claiming they work anywhere for those 15 or 18 hours a day, day after day.

Now, I don’t know about other educational courses, but anyone who’s done their engineering, or even sat through a 3-4 hour management ‘discourse’ would know how the brain just shuts off after a bit.
Or for that matter, even if you were busy working on a school or college project on a tight deadline, after hours of continuous work, am sure you would have realized that while it was perhaps possible to continue doing some monotonous mindless repetitions (say copying full paragraphs from one document to another), it was near impossible to do something creative or something that required you to reason.

I know for sure from personal experience. During engineering, I was up for 2.5 days straight during a week-long cultural event at college. And somewhere towards the end of that 2.5 days, some genius put me in charge of handling music for a group dance. And at any other time, I could operate the Winamp shortcuts blindfolded, but right there and then, I goofed, and stopped instead of pausing a track. Thankfully the highly skilled bunch of girls picked up from some random music position I started again, and they were big-hearted enough to spare me later too.
Anyway, so how is it humanly possible to go through those extra long work hour days without losing out on productivity and creativity?
Sure you’d probably manage to impress a superior who thinks ‘long work hours=value for money on employee salary’, but am sure others would realize what they are losing in the bargain, the purpose for which they had hired you in the first place.