Where will you be in 2091? It's safe for most of us to assume we won't be around. So here's a better question: What companies that exist today will still be around in 2091? 

Even if money won't bring you back from the grave when that year comes around, starting your due diligence by asking the latter question can lead to much better investment decisions. That's because the companies that survive that long will have the power of compounding working in their favor, producing market-thumping results.

An alarm clock on a picnic bench

Image source: Getty Images.

Here, three of our investors here at The Motley Fool will tell you why they think Welltower (NYSE:WELL)Boeing (NYSE:BA), and Amazon.com (NASDAQ:AMZN) are all worth buying and holding for the next 75 years.

An incredible long-term growth opportunity

Matt Frankel (Welltower): Welltower is the largest real estate investment trust, or REIT, that specializes in healthcare properties. This could be an excellent way to invest in the aging U.S. population, while generating a rock-solid income stream at the same time.

The company owns 1,384 healthcare properties, about 70% of which are senior housing facilities. Most of the properties are located in the United States, but the company has substantial investments in the U.K. and Canada as well.

To make a long story short, because of the ongoing retirement of the baby boomer generation and longer life expectancies, the older age groups of the population are expected to grow rapidly in all three of Welltower's markets. The senior citizen population (ages 65 and up) is expected to roughly double between now and 2050, and the 85-and-above age group -- the group most likely to utilize senior housing -- is expected to grow significantly faster than that.

Welltower has a 46-year track record of delivering strong results and dividend growth to its investors, with a 15.5% average annualized return since inception, and a nearly perfect history of increasing its dividend, which currently translates to a 4.6% yield. While a company's past performance is certainly not a guarantee of its future returns, with the favorable demographic trends, there's no reason to believe Welltower won't continue to outperform.

Book a flight on this defensive stock

Rich Duprey (Boeing): Aerospace and defense contracting giant Boeing is going to be around for a long, long time to come. While it is a cyclical business and it's been flying high since the recession, Boeing could still have plenty of altitude left in its stock, particularly over the next 75 years.

Arguably best known for its hugely popular 737, as well as the 747, a plane Boeing first introduced in 1970, the 787 Dreamliner widebody has garnered much of the attention because of its audaciousness -- though it ultimately serves a limited market. But there's also a new 400-seat aircraft -- the 777X -- that's still on the drawing board, and it could become the biggest-selling airplane in the market after its first delivery in 2020.

Currently the sweet spot for aircraft manufacturing remains the 737, where Boeing has a backlog of over 4,500 plane orders. Even as it builds them at a rate of 42 per month, it expects to incrementally increase that number to 57 per month by the end of the decade.

As important as the commercial-aircraft market is, let's not forget the defense-contracting side of the ledger, where Boeing continues to add new contracts for military aircraft, both here and abroad. From fighter jets to maritime observation craft, Boeing goes hand in hand with the country's military budget, which, particularly these days, may see significant increases.

That's not likely to change of the coming decades, and where companies such as Lockheed Martin will be both competitor and partner at times, and upstarts such as SpaceX will also enter the picture, investors can rest assured that Boeing will remain a constant. With a dividend that's currently yielding 2.2% because of its price, 75 years from now, Boeing stock will be looking back at us from the stratosphere.

Bet on the things that don't change

Brian Stoffel (Amazon.com): When asked to form a prediction of the future, best-selling author and former trader Nassim Taleb said he focuses on the things that don't change -- not the things that do. He calls it the Lindy effect: Non-perishable things that have lasted for a long time are very likely to continue lasting a long time. Think of War and Peace versus the most recent addition of People magazine. Which will people still be reading in 10 years? You get the idea.

While Amazon hasn't been around as long as a lot of other companies out there, there's something that gives me confidence about its survival: It focuses on the things that don't change. Here's what CEO Jeff Bezos has to say:

We know that customers want low prices, and I know that's going to be true 10 years from now. They want fast delivery; they want vast selection. It's impossible to imagine a future 10 years from now where a customer comes up and says, "Jeff I love Amazon; I just wish the prices were a little higher," [or] "I love Amazon; I just wish you'd deliver a little more slowly."

The basis for that viewpoint comes from the company's simple mission statement: "to be the earth's most customer-centric company." I believe customer service will always be in demand. As long as Amazon can keep this point front and center, I believe it will thrive for decades.

Brian Stoffel owns shares of Amazon. Matthew Frankel has no position in any of the stocks mentioned. Rich Duprey has no position in any of the stocks mentioned. The Motley Fool owns shares of and recommends Amazon. The Motley Fool recommends Welltower. The Motley Fool has a disclosure policy.