Forever is a very long time. The Dow Jones Industrial Average index had 20 members 100 years ago. All 20 fell off the index over the last century and all of the current Dow 30 members came in along the way. That might sound like a harsh evaluation of an index that's supposed to represent the best of the best, but that's just life -- times change and it's hard to keep up over a span of decades or centuries. Not even Warren Buffett hangs on to every stock until the end of time.

So, when I say that you should hold Tesla (NASDAQ:TSLA) shares forever, you should take that suggestion with a few sodium chloride crystals. What I mean is, it's a great idea to pick up some Tesla stock today and hold on for the foreseeable future. Here's why.

1. Model 3 is the best electric car of 2020

Consumer Reports recently named the Tesla Model 3 as the best electric car available in 2020. That's impressive because Tesla's earlier success has inspired a plethora of rivals to come up with their own electric vehicles, led by names like the Nissan Leaf and General Motors' (NYSE:GM) Chevy Bolt. And if that weren't enough, used-car vendor iSeeCars found that a new Model 3 holds its value better than any other car. The runner-up Ford (NYSE:F) Ranger is hitting the used market roughly 11% below its sticker prices while the Tesla 3 can be resold at a mere 5.5% discount.

2. But Tesla is not really a carmaker...

When you go to Tesla's investor relations site, the first sentence you'll see is this: "Tesla's mission is to accelerate the world's transition to sustainable energy."

The company description then goes on to explain how electric cars help the company achieve this overarching goal, but make no mistake: Tesla is a renewable energy company first and a car company second.

3. This company wants to change the world -- for the better

Oh, don't take my word for it. I'll just quote the investor relations site's company description again:

"As the world's only fully integrated sustainable energy company, Tesla is at the vanguard of the world's inevitable shift toward a sustainable energy platform."

Along the way, Tesla also aims to save thousands of human lives by equipping its cars with fully functional self-driving systems.

4. A secret mission that's no secret at all

CEO Elon Musk published "The Secret Tesla Motors Master Plan" in 2006, two years before the first Roadster rolled off the assembly line. That 1,300-word document boils down to this pithy bullet list:

Build a sports car

Use that money to build an affordable car

Use that money to build an even more affordable car

While doing above, also provide zero-emission electric power generation options

If that sounds familiar, it's because Tesla executed this exact plan for 10 years. In 2016, Musk published his "Master Plan, Part Deux," with the following goals for the next phase of Tesla's history:

Create stunning solar roofs with seamlessly integrated battery storage

Expand the electric-vehicle product line to address all major segments

Develop a self-driving capability that is 10 times safer than manual via massive fleet learning

Enable your car to make money for you when you aren't using it

The company stands in the middle of this phase today. I can't wait to see "Part Trois" in a few years.

5. It knows how to grow

Tesla delivered 101,000 cars in 2017, generating $11.8 billion of top-line sales while consuming cash to the tune of $4.1 billion in negative free cash flow. Fast-forward to 2019, where the less expensive Model 3 helped Tesla reach 367,000 delivered vehicles during the year. Revenue more than doubled to $24.6 billion and the company generated a cool $1 billion of positive free cash flow.

Musk waxed poetic about his company's huge growth rates in Tesla's fourth-quarter 2019 earnings call.

"It's hard to think of another company that has a more exciting product and technology roadmap," Musk said. "If you look back 10 years from today to 2010, we will produce approximately 1,000 times more cars in 2020 than we produced in 2010 and we have also Solarglass and solar retrofit and Powerwall, Powerpack, all those things too. So where we will be in 10 years, very excited to consider the prospect."

6. Gearing up an impressive cash machine

Model 3 allowed Tesla to ramp up its manufacturing processes dramatically, achieving economies of scale it never had before and producing generous cash flow to boot. The upcoming Model Y and Cybertruck models are poised to amplify that effect, continuing Tesla's skyrocketing revenue growth and bolstering the company's cash flow.

7. Have you seen the Cybertruck?

Tesla could have entered the light truck market by slapping electric engines into a chassis built like a Ford F-150 or Chevy Silverado. That's not what happened. The Cybertruck looks nothing like an old-school pickup truck, and that's by design.

"We tried to build a product that is superior in every way without any preconceptions of how such product should look," Musk said. "We wanted it to look like something that just came out of the site of a movie set from the future."

8. Not done building Gigafactories

Tesla's Gigafactory in Nevada is the largest lithium-ion battery factory in the world. The company already opened a second Gigafactory in Buffalo, New York, which produces photovoltaic modules and solar cells. More Gigafactories are under construction in Shanghai and Berlin, going back to the battery-production idea. And I think we'll see a lot more of these factories popping up over time. After all, Musk has said that it would take roughly 100 battery-focused Gigafactories in order to produce enough energy storage to let solar cells replace all other forms of energy production.

9. Tesla's electronics are years ahead of the competition

Nikkei Asian Review recently performed a teardown of the Tesla 3 and its electronic components. The Japanese business paper's engineers were shocked over the advanced circuits they found inside the car. An engineer from an unnamed rival car company looked at the central control unit and conceded that his company "cannot do it."

The systems in current Tesla vehicles should be able to achieve full self-driving capabilities with the right programming. That's level 5 autonomous driving in a classification system that stretches from levels 0 to 5. For now, Tesla's autonomous driving features stand at level 2, which still requires a fully alert human driver. Other automakers don't expect to put level 5-capable electronics in their cars until 2025, giving Tesla a six-year head start. Nikkei said that other car companies are subject to long-standing component supply contracts that make it difficult to make truly drastic improvements to any part of their cars. As a much younger company without decades of industry baggage, Tesla just doesn't have that problem.

10. Advertising budget: zero dollars

Word of mouth is working very well for Tesla. Let me pull up the latest annual report for this one (emphasis added):

"Historically, we have been able to generate significant media coverage of our company and our products, and we believe we will continue to do so. Such media coverage and word of mouth are the current primary drivers of our sales leads and have helped us achieve sales without traditional advertising and at relatively low marketing costs."

11. This business culture is built to last

Tesla's stated goals include to move fast, do the impossible, constantly innovate, and think like owners. That's a philosophy I can get behind, combining audacious ambition with the sober responsibility that comes from thinking like an owner. Tesla has some massive goals in mind and this philosophy was built to manage ambitions of an epic scale.