While time in the market is more important than timing the market, sometimes being a little patient is the key to finding a bargain. Right now, you'll pay a pretty penny to invest in high-powered growth stocks, but if you're willing to watch carefully for a few months or even the better part of a year, it might be possible to find a better deal. Similarly, sometimes a company needs a little more time to cook before it's stable enough to be investable, and the only way to know when it's ready is by paying attention over time.

With that in mind, let's review three such growth stocks that I'll be watching very closely this year.

1. Eli Lilly

Eli Lilly's (LLY 1.19%) 2024 is going to be a bumper crop year. As a result of its hit type 2 diabetes drug Mounjaro and its twin sibling called Zepbound, which is indicated for weight loss, it's hard to see this pharma doing anything other than raking in loads and loads of money. The market's expectations for the success of those two medicines are so strong that even the company's explicit rejection of the idea of using either for "cosmetic" weight loss -- a gargantuan market -- did nothing to stop the upward march of its shares.

What's more, management is intent on keeping the party going in terms of deepening its penetration of the diabetes and obesity therapies markets. It has nine programs in late-stage clinical development for treating those conditions. Analysts on Wall Street are calculating on average that it'll report more than $39 billion in sales for 2024, a massive increase from its revenue of $28.5 billion in 2022. In that light, it's no surprise that Eli Lilly's price-to-earnings (P/E) ratio is a sky-high 116.

With a bloated valuation like that, the company will either need to maintain its hectic pace of growth or its shares will need to come down in price, eventually. If the latter happens, there's a good chance it'll be a smart move to buy its shares before the next leg up.

2. Ginkgo Bioworks

Ginkgo Bioworks (DNA 10.60%) is a biotech that's positioning itself to be a best friend to other biopharma businesses. To accomplish that, its platform uses artificial intelligence (AI), machine learning, robotics, and a boatload of industrial laboratory automation to streamline the process of developing and manufacturing bio-engineered organisms like yeast, viruses, or bacteria. By making such a complicated process considerably less painful and expensive than it would be otherwise, the company's goal is to keep finding more and more customers so as to reap the benefits of economies of scale.

That all sounds great, assuming it can be done profitably. That's the reason why Ginkgo is worth watching carefully. Despite its successes in attracting customers to its platform over the last couple of years, it's still burning money, and its trailing-12-month (TTM) operating margin continues to be deep in the red. If that starts to change, which the company will need to if it is going to succeed, it could be a signal that it's becoming ripe for a buy. Until then, it's on the watchlist for frequent review.

3. Costco

Costco Wholesale (COST 1.01%) is worth watching because it's a proven wealth-builder stock that's ripe for holding over very long time periods. Thanks to its stellar business model in which it charges people an annual membership fee for access to its warehouses where they can buy dirt-cheap groceries and consumer goods of decent quality in bulk, its TTM net income is up by 232% over the last 10 years, reaching $6.5 billion. Unless people get tired of buying everything from gasoline to T-shirts to tenderloin at lower prices than they'd get elsewhere, the company's next 10 years are likely to be just as thrilling for investors.

Therein lies the problem: Everyone recognizes that Costco is a quality business to own and that it won't be going anywhere. Costco's shares trade at a P/E of 45, which is far above the wholesale industry's average P/E of 24. And given that it's opting to pay out a special dividend of $15 per share on January 12, it's clear that management thinks it has more than enough cash to invest in growth and pay off investors at the same time -- a highly bullish sign.

So, while it's unlikely that there's any big dip coming, I'll be on the lookout for opportunities to load up on more shares.