In the end, investors buy stocks to make money. When a stock is up big, it's tempting for some to "pull money off the table" and sell some shares. But that could be a big mistake. On a Fool Live episode recorded on June 30, Fool contributors Brian Feroldi and Brian Withers discuss programmatic advertising leader The Trade Desk's (NASDAQ:TTD) most recent results and whether investors should sell after the big run-up in the share price.

Brian Feroldi: Let's move on to The Trade Desk, ticker symbol TTD. This is an online platform for helping brands and ad agencies to get better bang for their ad dollar. This company has been a rocket ship since its IPO and it had a fabulous first quarter.

Revenue grew 37% to $220 million. That blew away management's expectations. Its customer retention rate remained over 95% for the fifth year-plus in a row. Gross margin expanded a little bit to 77%. The expenses were up quite a bit, but almost all of that was related to stock-based compensation in part to the company's exploding share price. On an adjusted basis, net income -- yes, this company is profitable -- grew 56% to $70 million or $1.41 per share. The balance sheet remains pristine, $608 million in cash and no debt.

What's great news for investors? The company saw faster growth of its connected fitness [TV] products in Europe and Asia than it did in the US. The management team thinks that it has enormous runway for its product abroad and it's been making investments in that for years. It's nice to see those things start to pay off.

It also launched a new partnership with Walmart that's going to provide advertisers with the data to Walmart's shopping experience and sales measurement data. I mean, that's an incredible resource that should make this platform even more powerful for brands.

Now, management thinks that in the upcoming quarter is going to be even better. They're projecting 87% revenue growth at the midpoint. Part of that is because of the year-ago period was the COVID quarter when their sales actually declined. So that's still really impressive overall. Another thing to note, this stock just recently split 10-for-1. If you're looking at the share price and saying, "what the heck," that's what happened.

Brian Withers: Yes, so even after the 10-for-1 split, my Trade Desk shares are up an average of sevenfold. For those who have held since early 2018, they're up even more. It's really hard to look at such a big gainer and go, is it time to take some money off the table with this stock? Especially with the recent bump with the Google cookie announcement pushing out to 2023.

Feroldi: So my answer to that would be, The Trade Desk is currently a $37 billion business. The margins are high, revenue is recurring, they're taking market share, their TAM is enormous and they are having success in just about everything. That is a textbook stock I do not want to sell ever. Hopefully.

So could this company be worth $100 billion in someday, $200 billion in someday? It's entirely possible. I mean, Google, which is primarily an ad-based model that's worth what? One point something trillion. Facebook just crossed $1 trillion. I think there's room for this company to grow between it's $40 billion market cap and those tech giants.

Withers: Yeah. I know Brian when you and I talk about our biggest mistakes in investing, it's all about selling too soon. Those can be several common mistakes.

Feroldi: All the biggest mistakes I've ever made are selling awesome companies early. [laughs] Every other mistake pales in comparison to that mistake.

Withers: Yes. I agree. I'm holding my Trade Desk shares.

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.