Amazon (AMZN 0.58%) CEO Jeff Bezos has retained his start-up mentality. He runs one of the most successful retailers in the world, yet he keeps his company focused on the idea that it's had from day one.

That's a philosophy that Bezos regularly references. It's detailed in a letter he wrote in 1997 that he continues to attach to each year's annual report. 

But this is Day 1 for the Internet and, if we execute well, for Today, online commerce saves customers money and precious time. Tomorrow, through personalization, online commerce will accelerate the very process of discovery. uses the Internet to create real value for its customers and, by doing so,hopes to create an enduring franchise, even in established and large markets.

Even though it's 23 years after Bezos wrote that letter, the underlying ideas still apply. That's at the core of why Amazon may be the perfect long-term investment for your retirement portfolio.

An Amazon drone

Amazon has invested in technology including drones that will eventually pay off. Image source: Amazon.

Building for the future

Many public companies manage for the next quarterly report. Management may worry about spooking shareholders, or even getting fired, if they have a down quarter.

That type of thinking values the present over the future. A company that's being managed to deliver good quarterly results may not be making the investments needed for long-term success.

Amazon has never been run that way. Bezos has the advantage of being his company's founder, not just its CEO. Because he owns a controlling interest in the online retailer, Bezos does not have to make short-term decisions in order to protect his job.

That has allowed him to make bold bets. The most recent example is his decision to move from a two-day shipping standard to one-day. Consumers arguably weren't asking (at least overtly) for that. Bezos understood, however, that it was important to stay ahead of his rivals and give customers better service, even if they weren't demanding it.

Efforts like this tie to a section in the 1997 letter. Under the headline "it's all about the long-term," Bezos laid out the underlying philosophy that continues to guide the company.

"We believe that a fundamental measure of our success will be the shareholder value we create over the longterm," he wrote. "This value will be a direct result of our ability to extend and solidify our current market leadership position. The stronger our market leadership, the more powerful our economic model. Market leadership can translate directly to higher revenue, higher profitability, greater capital velocity, and correspondingly stronger returns on invested capital."

It's always day one

Your retirement portfolio does not just need stocks that perform well today. It should also be filled with companies that are investing for long-term success, and Amazon epitomizes that philosophy.

Bezos' 1997 letter explained that the company would "continue to focus relentlessly on our customers." He also pledged to focus on "long-term market leadership considerations rather than short-term profitability considerations or short-term Wall Street reactions."

That's what you want as an investor -- a company that's constantly focused on tomorrow. Amazon will have bad quarters, even bad years, but that's not what's important. The company is making the moves needed to keep it ahead of the pack in retail for decades to come.