Source: Netflix.

My retirement portfolio contains 17 different stocks. But it's hardly an equal-weighted collection, because the top three holdings add up to 47% of the entire portfolio's current worth. Let me tell you why I'm comfortable focusing so tightly on Netflix (NASDAQ:NFLX), Alphabet (NASDAQ:GOOG) (NASDAQ:GOOGL), and Walt Disney (NYSE:DIS).

Cards on the table
Six percent of my holdings are currently invested in Disney shares. I have built this position through a couple of separate buy orders over the last two years. I'm looking at an aggregate return of 20%, while the S&P 500 benchmark only increased by 8%.

Another 8% block sits in Alphabet's Class A shares, the kind that comes with voting powers. The position was started more than five years ago. When the stock split into A and C shares, I promptly sold my C stubs to reinvest into the Class A ticker instead. That move has boosted my overall Alphabet return by a piddling 0.7% so far, but that was never the point -- I take stock ownership seriously and insist on voting even if insiders have an iron grip on every election. All told, my Alphabet stake has outgrown the S&P 500 by a margin of 128% to 59%.

As for Netflix, I took my profits on a five-year-old holding in 2009, when the DVD model was starting to look limited. Then I jumped back in early 2010, as the online streaming model started to crystallize. Like everyone else, I took my lumps when the Qwikster debacle reared its ugly head, and I bought more when CEO Reed Hastings proved that he could make us forget about that misadventure. With a composite return of more than 460% on these modest investments, Netflix now accounts for 33% of my overall portfolio.

A digital view from Google's offices in Amsterdam. Photo: Google.

What makes these stocks so special?
Let me make it clear that I plan to own all three of these stocks for a long time. They are, in my opinion, the kind of investments you can stick under your mattress and forget about for the next decade or more.

Specifically, I expect Disney to deliver powerful and stable growth as long as the House of Mouse keeps trusting the creative geniuses from Pixar and Marvel. I'll keep an eye on how the company is run, but Disney has done absolutely nothing so far that would make me think the company is run by creativity-stifling committees.

Alphabet is a centennial conglomerate in the making. We are only watching the company outgrow its online search roots and make its first few moves into even meatier business prospects. From serious healthcare research to potentially remaking how we think about transportation, the company formerly known as Google is changing the world for the better.

Finally, Netflix might have the shortest path to an endgame but that exit is still many years away. The innovative DVD mailer model gave way to an even more convenient digital streaming model. That service has now gone global. In 2017, Netflix management plans to shift from an all-out subscriber growth sprint and into a more profitable structure. The stock has soared 500% higher over the last four years, but the real payoff will come when investors get to see big bottom-line profits. So I'm in for the next few years at least, and then we'll see what Hastings plans to use Netflix's growing bank balances for.

What's next?
Netflix and Disney are currently taking a breather from their strong long-term returns. I expect them to get back to pulling their weight soon enough, and have no plans to sell them. Why liquidate your winners, when you expect them to keep winning?

It would be nice if the other 14 stocks under my wing could put their game faces on and start catching up. If I didn't think they have what it takes, I'd be selling them and reinvesting elsewhere. But these are my three biggest bets today. Netflix and Google grew into their huge boots, while I shoveled a somewhat larger opening investment into Disney.

And I'm quite comfortable leaning on these robust businesses for the long run.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.