Buy and hold. It's an easy strategy to understand. But it's a really hard one to consistently follow for many investors. However, with the right stocks, the approach can generate tremendous long-term returns.

Three Motley Fool contributors have identified stocks to buy and hold forever. Here's why they chose Eli Lilly (LLY 1.30%), Novo Nordisk (NVO 2.99%), and Vertex Pharmaceuticals (VRTX -2.02%).

A solid business with strong growth potential

David Jagielski (Eli Lilly): If you're planning to hold a stock forever, then you need to be comfortable with its growth potential. And that's exactly why Eli Lilly belongs on this list. The company not only has many top drugs in its portfolio today, but it also has a promising future that could drive revenue for the business for years to come.

The company recently released its second-quarter results. Multiple drugs generated growth of at least 25% or more. The list includes Lilly's top-selling diabetes medication, Trulicity. Through the first six months of the year, the company's total sales increased by 6% year over year and operating profits jumped by 41%. Eli Lilly's stability is a key reason why it has been a safe stock to hold this year -- it's up close to 10% while the S&P 500 has nosedived more than 10%.

But what investors should be most bullish about is Lilly's future. The U.S. Food and Drug Administration (FDA) recently issued two key approvals for the company: Olumiant (baricitinib) for treatment of alopecia areata (patchy hair loss) and Mounjaro for treating diabetes. In addition, four other of Lilly's candidates are under regulatory review, including experimental Alzheimer's disease drug donanemab, which is among the company's most promising experimental therapies. Lilly also has another 20-plus trials ongoing that are in phase 3.

Lilly's strong financials can help accelerate its business prospects even further. The company is highly profitable, with profit margins of around 20% of revenue. That's important because it allows Lilly to be able to use those profits and reinvest in its business over time or pursue acquisitions. Those strong fundamentals should give investors confidence that this is a safe stock to invest in for the long haul.

A storied past and a promising future

Prosper Junior Bakiny (Novo Nordisk): Drugmakers like Novo Nordisk have a distinct advantage in staying relevant in challenging economic times and over the long run. Whereas many industries can fall out of favor as time goes by, lifesaving medicines will remain in high demand.

Still, to remain profitable, Novo Nordisk will have to continue innovating. There is ample evidence that the Denmark-based pharma giant can do that. Novo Nordisk has been a leader in the market for diabetes drugs for a long time. As of May, it held a 31% share of this market, an increase of 1.4% compared to May 2021. And Novo Nordisk executive Camilla Sylvest said on the company's second-quarter earnings call that its market share in GLP-1 (glucagon-like peptide-1) diabetes drugs tops 61%.

Novo Nordisk has also delivered superior market returns over the past several decades, partly thanks to its strong position in diabetes care. There are excellent reasons to think it can continue down that path as it boasts several promising candidates in its main therapeutic area. The company recently announced solid results from a clinical trial for icodec, a potential once-weekly insulin product for type 2 diabetes.

Patients typically take insulin daily. A once-a-week option could make their lives substantially easier. Novo Nordisk's prospects in this field look even brighter, considering researchers have projected that the percentage of the population with diabetes will rise rapidly in the coming decades. This unfortunate fact emphasizes the need for innovation in diabetes care, and Novo Nordisk is arguably at the forefront of that.

Meanwhile, the company has sought to increase its presence in other therapeutic areas. It is currently running eight late-stage studies targeting Alzheimer's, hemophilia, and other indications not related to diabetes or obesity. All these things (and more) point to an exciting future for this top drugmaker. 

A game-changing big biotech

Keith Speights (Vertex Pharmaceuticals): It's no exaggeration to say that Vertex Pharmaceuticals has been a game changer for thousands of cystic fibrosis (CF) patients across the world. The company's CF drugs are the only ones approved to treat the underlying genetic 

I think this biotech stock can be a game changer for investors who buy and hold as well. Vertex is already trouncing the broader market in 2022 thanks in large part to its strong revenue and earnings growth. But the company has a lot more growth likely on the way.

As a case in point, Vertex and CRISPR Therapeutics expect to file for regulatory approvals in Europe by year-end for exa-cel. The companies are in discussions with the FDA about regulatory submissions. Exa-cel holds the potential to provide a one-time cure for patients with two rare blood disorders, sickle cell disease and transfusion-dependent beta-thalassemia.

Vertex also has two other promising programs that are either already in or soon will be in late-stage development. Inaxaplin (VX-147) targets APOL1-mediated kidney disease. This indication has a bigger patient population than CF does. The company is branching out beyond genetic diseases with VX-548, a non-opioid treatment for acute pain.

Don't overlook Vertex's early-stage type 1 diabetes program, though. The company believes that it will eventually be able to cure the disease that impacts close to 2 million Americans.

Last, but not least, Vertex still has opportunities in CF. Currently, a little over half of the estimated 83,000 patients with CF benefit from the company's therapies. Vertex expects to significantly increase its market share over the next few years by securing additional reimbursement deals and winning new regulatory approvals. It's also developing a new gene-editing therapy that could treat the 5% of CF patients who can't benefit from its current drugs.