Cliche as it may be, love is in the air -- but I'm not talking about Valentine's Day. I'm talking about investors' ongoing love affair with equities.

This past Tuesday, Feb. 9, all three major U.S. indexes jumped to record intraday highs, including the tech-heavy Nasdaq Composite, which closed above 14,000 for the first time ever. Despite a nearly two-decade high in the S&P 500's Shiller price-to-earnings ratio, investors remain undeterred by the stocks they love.

If you're a committed long-term investor with cash to spare, consider putting it to work in the following five stock market sweethearts.

An assortment of candy hearts with various Valentine's Day-based sayings etched on them.

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Pinterest

Nothing says amore quite like 459 million monthly active users (MAU) willingly posting about the people, places, products, and services that interest them. That's why social media up-and-comer Pinterest (NYSE:PINS) is a stock you'll want to grab hold of and never let go.

Prior to the coronavirus disease 2019 (COVID-19) pandemic, Pinterest's MAUs had been growing by an average of 30% between 2017 and 2019. In 2020, with people stuck in their homes and turning to the internet for entertainment, Pinterest shone brightly. The company added a net of 124 million MAUs (37% year-over-year growth), with more than 90% of these new net additions coming from outside the U.S. 

On the one hand, international MAUs generate substantially lower average revenue per user (ARPU) than U.S. MAUs ($0.88 vs. $15.34 in full-year 2020). Then again, the ability to grow ad revenue in overseas markets and double international ARPU many times over is precisely why Pinterest is growing so quickly and crushing Wall Street's expectations.

Furthermore, Pinterest is still scratching the surface when it comes to its e-commerce ambitions. With its users willingly sharing their interests, Pinterest can be the intermediary between these motivated consumers and small businesses. It's already partnered with cloud-based e-commerce platform Shopify to aid small businesses in optimizing their sales potential. Pinterest has also reworked multiple aspects of its website to streamline the buying process.

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NextEra Energy

Another stock market sweetheart bound to lead to an electric connection is electric utility stock NextEra Energy (NYSE:NEE). NextEra is the largest electric utility by market cap in the U.S.

Traditionally, utility stocks are defensive (i.e., borderline boring) businesses that rely on steady demand to grow by low single-digit percentages. But there's nothing traditional about NextEra, which is leading the pack in renewable energy projects. No utility stock is generating more capacity from solar or wind than NextEra, with the company spending up to $55 billion between 2020 and 2022 on new infrastructure projects. It also anticipates installing 30 million additional solar panels in Florida by 2030 to generate at least 10,000 megawatts of capacity.

The downside of tackling these renewable projects is that they're pretty costly. NextEra ended the previous quarter with $48.1 billion in total debt, much of which has financed this shift away from fossil fuels. However, access to capital is historically cheap at the moment. Plus, the company's substantially lower electric generation costs have allowed it to consistently grow by a high single-digit percentage.

As the icing on the cake, NextEra's nonrenewable utility operations are regulated, which is a fancy way of saying that price hikes need to be approved by a state's public utility commission. Though that might sound restrictive, it ensures that the company isn't exposed to potentially volatile wholesale price swings.

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Cresco Labs

Nothing says "smoking-hot" on Valentine's Day quite like marijuana stocks. While the entire industry has been blazing higher for weeks, the one pot stock that should be getting a lot more respect is multistate operator Cresco Labs (OTC:CRLBF).

Cresco has 20 operating dispensaries at the moment, but it could expand that number if its acquisition of Bluma Wellness closes. For now, 10 of the company's retail locations are in the limited license state of Illinois. With a set number of dispensary licenses being issued, Cresco's maximized presence in this billion-dollar niche should yield significant market share.

However, the bigger bang for Cresco's buck is coming from its wholesale operating segment. Even though wholesale produces smaller margins than retail pot, the company has more than enough volume to make up for this margin difference. That's because it holds one of the few cannabis distribution licenses issued by California, which is the largest marijuana market in the world by annual sales. Cresco already has access to more than 575 dispensaries throughout the state, and this figure should continue to climb over time.

Currently sporting one of the lowest price-to-sales multiples among multistate operators, Cresco Labs looks like a bargain.

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Mastercard

If you want another way to get charged up on Valentine's Day, look no further than payment processing giant Mastercard (NYSE:MA).

Buying into the Mastercard growth story will get you no points for originality, but it's a winning long-term bet given the steady growth of the U.S. and global economy. Mastercard generates revenue based on the amount of payment volume traversing its network. As long as businesses and consumers are spending more, its profitability ticks higher. Since recessions are measured in months and periods of economic expansion in years, Mastercard is the perfect stock for patient investors.

Steering clear of lending has also helped Mastercard succeed. Mastercard may miss out on potential interest income, but it also doesn't face any direct negative impacts when delinquency rates rise during economic contractions and recessions. Not having to set aside capital for loan losses is a big reason why its profit margin is always so high (over 40%).

Despite Mastercard's size, its growth story still has legs. Since most global transactions are still being conducted in cash, the opportunity to push cashless payments gives the company low double-digit growth potential.

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Fastly

Last but not least, long-term investors should ask high-growth tech stock Fastly (NYSE:FSLY) to be theirs forever. Fastly helps secure and expedite the delivery of content to end users.

As you might imagine, Fastly was one of the prime beneficiaries of the COVID-19 pandemic. Consumers and businesses are increasingly moving online. A big uptick in traffic is a boon for Fastly's usage-based operating model. 

Fastly also managed to quickly put concerns to rest. As some might recall, Fastly modestly lowered its third-quarter sales expectations in early October after TikTok parent ByteDance removed most of its traffic from Fastly's network. This happened to be when TikTok drew the ire of the Trump administration. Though Fastly's stock briefly took it on the chin, the company's third-quarter operating results featured a 147% dollar-based net expansion rate. In layman's terms, existing clients spent 47% more than they did in the prior-year quarter. This ability to retain and scale with its existing clients will drive Fastly significantly higher. 

Don't be surprised if Fastly's revenue triples over the next four years.