Well, let’s look at the facts. On paper, Apple CEO Tim Cook has had a great run since taking over in Cupertino, CA, after the death of longtime CEO Steve Jobs in 2011. At press time, shares are up well over 100% since then. Cook has taken on and won over hard-nosed activist investors who questioned his direction of the company, such as Carl Icahn. And Apple remains the crown jewel of Silicon Valley. Frankly, most CEOs would give their right arm for Cook’s stock performance.

At the same time, however, shares have traded largely flat over the past year, and that’s because Cook can’t seem to kick the innovation knock. Analysts and investors continue to worry about the next Apple product and scoff at what Cook is saying about the future, like his recent musings about an Apple self-driving car.

I fear that Wall Street is always right about such things, and I’m pretty sure investors sold Jobs short more than a few times over the years, but there’s a good reason why investors remain skeptical about Tim Cook, and that reason should give anyone who wants to load up on Apple stock, particularly at these levels, some pause. It’s completely fair if you’re an investor in the stock and are wondering whether to load up on more or take your winnings now—because it remains to be seen whether Apple’s best days are ahead of or behind it.

Charles Gasparino is a Senior Correspondent at Fox Business Network. Follow him on Twitter.