Growth stocks often turn out to be multibaggers, as the market willingly pays a premium for companies with huge potential backed by sustainable competitive advantages or even by products or services in the making that could be game changers. Growth stocks, however, can also be risky. You need a really compelling argument that the long-term returns will far outweigh the risks so that you could make tons of money by owning these stocks for decades.

Three of our Motley Fool contributors see big growth potential in Five Below (FIVE -2.71%), TPI Composites (TPIC), and Amicus Therapeutics (FOLD 1.88%). Here's why.

Don't give a cold shoulder to Five Below

Rich Duprey (Five Below): Who knows what the value of a dollar will be in 50 years (probably not much), but deep-discount retailer Five Below will undoubtedly still be serving its teen and tween customers -- though by then it might be called Fifty Below.

The variety discount store has found a unique niche that really has no competitors. Most dollar stores' target customers are adults looking to stretch their cash, not kids being introduced to their first taste of consumerism. One of the great advantages of Five Below is that because all of its merchandise is priced at $5 or less, parents have few reservations about allowing little Timmy or Sally to run amok in the stores. The kids can satisfy their need for instant gratification, and parents won't spend much overall.

Wooden blocks placed on an ascending curve and spelling out "growth."

Image source: Getty Images.

Thanks to a practice of stocking the trendiest items along with a stable of evergreen merchandise, sales have been hot, growing 23% in the fourth quarter even after subtracting for the extra sales week in the year-ago period.

Five Below also doesn't need to worry much about cannibalizing sales as it opens new stores and enters more markets. Because the items it sells are so cheap, parents don't necessarily go out of their way to shop there, so if another location opens relatively close by, it won't really steal any sales from an existing store.

At some point, maybe 50 years from now, Five Below will hit a saturation point, but until then, investors can sit back and enjoy the meteoric trajectory this growth stock is on.

Watch which way the wind is blowing

Neha Chamaria (TPI Composites): I believe renewable energy will only gain traction in coming decades as more countries across the globe ditch fossil fuels to fight climate change even as demand for energy rises. Wind energy is touted to be a key contributor. In fact, the U.S. Energy Information Administration (EIA) expects wind to be the largest source of clean energy in 2019 and 2020 in the U.S.

Given the prospects, investors might want to consider owning a stock like TPI Composites for the long term. TPI Composites doesn't generate power but manufactures composite wind blades. It currently counts some of the leading wind-energy companies in the world as its customers, some of which combined have already cornered half the global onshore wind energy market.

TPI's contract value hit a record high of $6.8 billion last quarter (note that the company will release its first-quarter numbers in May), and management believes that positions the company to even double its wind-blade sales by as early as 2021. That suggests incredible sales growth potential, which should eventually trickle down to its bottom line and drive the stock price higher. I don't see any reason why the company would face a slowdown in coming years unless wind energy becomes unfeasible.

To be sure, TPI's profits may not really take off, as wind-blade manufacturing is a capital-intensive business that may also require frequent upgrading of existing manufacturing models to meet customer specifications and needs. However, heady top-line growth is also typically characteristic of a growth company, and TPI is already profitable. Moreover, with the company already dabbling in lightweight vehicle technologies, TPI could increasingly seek alternative revenue sources, related to clean energy of course, to expand its portfolio. That should further strengthen TPI's investing thesis.

A shining star in the rare-disease space

George Budwell (Amicus Therapeutics): Companies that specialize in the development of drugs for rare diseases often turn out to be outstanding long-term growth vehicles for investors. Most of these drugs, after all, sport jaw-dropping profit margins and exceedingly long shelf lives. The only problem is that the market tends to build sky-high premiums into these stocks well before they even bring their first product to market. Fortunately, there are a few rare-disease plays bounding about this heated market that are undeniable bargains -- especially for investors with a long-term outlook.

Amicus Therapeutics, for example, has the pieces in place to deliver tremendous returns on capital for investors over the next half century. Turning to the details, Amicus' fairly new Fabry disease drug, Galafold, should generate sales of at least $500 million per year in the early part of the next decade. And if gene therapies don't disrupt the Fabry disease market, Galafold might even go on to reach blockbuster status toward the tail end of the 2020s, thanks to a combination of the steady price hikes and a growing patient population.

While this single commercial-stage drug arguably justifies Amicus' current market cap of $3.1 billion, the company has two other major growth drivers under its roof at present. Specifically, the biotech is developing a Pompe disease candidate called AT-GAA, and it also has an intriguing early-stage gene-therapy platform that's targeting a host of high-value rare diseases. Taken together, these two clinical programs could eventually produce another $3 billion in annual sales for the biotech.

All told, Amicus offers a compelling mix of near-term growth and deep value, which should appeal to investors who are willing to hold stocks for an indefinite period.