The stock market has performed extremely well recently, with the S&P 500 index higher by 17% over the past six months. Many stocks have done far better, doubling or more in that short amount of time.

A stock that has been an excellent performer can still be worth buying, despite the higher price. Here are three in particular that still look like exciting long-term investments despite rising by 100% or more over the last six months.

Laptop user cheering.

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These three stocks have doubled (or more) in just six months

Company (Symbol)

Industry

6-Month Performance

Pinterest (NYSE:PINS)

Social Media

116%

Boston Omaha (NASDAQ:BOMN)

Conglomerate

145%

Lemonade (NYSE:LMND)

Insurance

119%

S&P 500 (for reference)

N/a

17%

Data source: YCharts. Six-month returns as of 2/3/2021.

All three have performed well for good reasons. Pinterest gained over 100 million users in the past year, Lemonade's revenue has more than doubled, and some of Boston Omaha's key investments have performed very well.

There could still be plenty of room to climb

Although these stocks more than doubled in just six months, there could be plenty of room to grow in the years ahead. 

Pinterest still has a massive opportunity to monetize its user base, especially internationally. The average international Pinterest user generates roughly 5% of the revenue of its domestic users. Since over three-fourths of Pinterest's user base is international, even a small narrowing of the gap could be a game-changer. Plus, since Pinterest's main use case is a place people go for ideas, there are some natural e-commerce opportunities that the company has just started to explore.

Boston Omaha Corporation is often compared to an early Berkshire Hathaway, and it's easy to see why. The company's business model involves acquiring subsidiaries and other investments, which can then generate cash flow to acquire even more. In addition to growth opportunities in its main businesses (billboards, insurance, and rural broadband), Boston Omaha recently launched a SPAC called Yellowstone Acquisition. One of its larger investments, Dream Finders Homes, also just completed a very successful IPO. With a market cap roughly 0.2% of Berkshire's size, it could still have quite a long way to let its time-tested business model play out.

Last but certainly not least, insurance technology company Lemonade has taken its core markets of homeowners, renters, and pet insurance by storm, with gross earned premiums more than doubling in the most recent quarter. To put Lemonade's impressive growth into perspective, consider that the company just hit 1 million customers in a little over four years in business, an accomplishment that took State Farm and GEICO 22 and 28 years to achieve, respectively. However, Lemonade is just starting to dip its toes into the $800 billion term life insurance market, and that's the most exciting opportunity right now. If Lemonade can replicate its success and capture a large share of the life insurance market, the recent performance could be just the beginning.

These companies are long-term winners; invest accordingly

Investors must remember that a top-performing stock can continue to deliver strong results. It's a common mistake to say, "Well, this stock has done well, let's look for something cheaper." All three of these companies have impressive growth opportunities going forward. These stocks have gone up for solid reasons, and could certainly give the market reasons why they're worth even more.

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.