James Dyson first started building vacuums in 1979. A few years ago he told the story to Inc.'s Burt Helm: 

I'd purchased what claimed to be the most powerful vacuum cleaner. But it was essentially useless. Rather than sucking up the dirt, it pushed it around the room. I'd seen an industrial sawmill, which uses something called a cyclonic separator to remove dust from the air. I thought the same principle of separation might work on a vacuum cleaner. I rigged up a quick prototype, and it did.

But even after that lightbulb moment, it still took Dyson "15 years and 5,127 attempts" at making and testing prototypes before his bagless cyclonic vacuum first cracked the market, he wrote in yesterday's Globe and Mail. 

Of course, Dyson's 15 years of highs and lows are not uncommon in the world of consumer product innovation. The inventors of the Ziploc bag needed 17 years to crack the market. Other decades-spanning innovations include the barcode, e-Readers, and HDTVs. 

What's important is not merely that Dyson stayed patient and resilient in launching his vacuum. It's that he built a billion-dollar company whose engineer-friendly culture encourages radical experimentation--and the thousands of prototypes and decades of effort that real innovation requires. 

For example, in the halls of the Dyson headquarters in Malmesbury, England, there's what Dyson calls "the Dyson prototype archive." It's a showcase for many ideas that haven't yet made it to the market. Here's Dyson's description in the Globe and Mail of a prototype in the archive called the Dyson Fuel cell:

For three years, 10 engineers worked to adapt a Dyson digital motor so it could sit at the heart of a fuel cell. What resulted was a compact, lightweight and highly efficient digital motor, the V4HF digital motor, which resulted in a 20-per-cent increase in power density and improved efficiency. Whilst this technology hasn't yet found its perfect application, our findings were substantial and taught us much about digital motors--knowledge we are applying to our small, lightweight cordless vacuums.

In other words, the prototype archive offers two important takeaways for the company. The first is cultural: It shows the engineers that cracking the marketplace isn't everything. Yes, it's a key goal, but it doesn't mean it's the only reason an idea matters. The second is educational: Even products without market applications can teach engineers big lessons about high-tech efficiencies.  

Dyson adds that he prefers to hire inexperienced, young employees straight out of college. "Untried minds bring energy and expertise in places where, let's be frank, someone with my number of miles on the clock might not have," he writes. 

His recruiting philosophy--young, curious, mentally energetic and broadly educated--is similar to that of Carey Smith, founder of $122-million Big Ass Solutions, a designer and manufacturer of high-tech fans and LED lights based in Lexington, Ky. "Some of our best people are English majors," Smith once told me. "A liberal arts degree is a good thing. You're looking for people [who] are naturally curious, who want to know why. I love engineers; they're great. But with liberal arts majors, if they're really engaged and they really studied, they're curious."

For all of its success, Dyson remains a privately held company. Perhaps it's no wonder, then, that it has maintained a strong culture of innovation. Not long ago Clayton Christensen, the decorated Harvard Business School professor and expert on innovation, criticized public companies for acting more interested in "adorning their balance sheets" than they are in pursuing groundbreaking innovations.

Christensen's theories, which he's presented in New York Times editorials and longer HBR essays, center on this question: Why are public companies hoarding capital in an era when capital is plentiful? The answer, of course, is classic short-termism. Hoarding capital looks great on a balance sheet. Game-changing innovations, by contrast, usually don't. After all, those innovations usually take at least five years (and, as Dyson just revealed, sometimes as long as 15 years) to pay off.

How can you avoid the investor pressure to burnish a balance sheet? One way is to stay private, like Dyson has. Nor is Dyson alone in this decision. For some companies--both Big Ass Solutions and Edmonds.com come to mind--the prestige of going public just isn't worth the short-term-results pressure it's bound to bring. 

About one year ago, Fortune's David A. Kaplan asked Dyson if he'd ever considered going public. "Not seriously. It would be the wrong thing to do," he replied. "There would be a huge pressure on profits over investment in research and development."

And there you have it. Perhaps that's a lesson you never forget, when your first breakthrough took 15 years and 5,127 prototypes. "Designing something that works well requires careful thought and precise measures, then relentless testing and prototyping," writes Dyson at the conclusion of his Globe and Mail essay. "It takes time. Perhaps the biggest thing that holds invention back might be our impatience."