Source: Apple.

Coming into last month, longtime investors in Apple (NASDAQ:AAPL) had already gotten used to seeing big moves from the stock, as share prices had doubled from their mid-2013 lows as fears about erosion in its dominant mobile-device brand proved to be overblown. Yet as the world's most valuable company saw its market capitalization soar above the $700 billion briefly last week, further gains in Apple represent huge amounts of wealth, with November's better than 10% gain amounting to more than $60 billion in market-cap appreciation. Bullish investors can still point to fairly reasonable valuations for the iPhone giant, but those who are more nervous about the huge gains in their shares no doubt wonder whether the stock has come too far too quickly. Let's take a closer look at the factors that helped send Apple stock skyward in November and whether even better times for the Mac-maker remain ahead.

AAPL Chart

AAPL data by YCharts

What's behind the Apple surge?
Much of the gain in Apple shares came from follow-through after the company's fiscal fourth-quarter earnings report in late October. Revenue climbed more than 12% to $42.1 billion, easily eclipsing Apple's previous guidance for $37 billion-$40 billion in sales. Earnings per share soared an even more impressive 20%, and Apple's guidance for the current quarter was also much more optimistic than investors had expected before the report.

Source: Apple.

In response, Wall Street analysts have made ever-rosier predictions about how much higher Apple stock could soar. The big wildcard for the current quarter is just how many of its iPhone 6 and iPhone 6 Plus devices Apple can sell, as most investors have already taken into account early sales figures regarding the newest members of the iPhone family. Yet even looking beyond the iPhone 6 product cycle, the discovery that Apple can introduce larger Plus smartphone models with advanced features while still driving demand for its traditional iPhone line could lead to parallel tracks for future releases, multiplying Apple's profit potential by tapping into every conceivable source of smartphone customer demand.

Also around the corner is the launch of the Apple Watch, which many have seen as the next major direction for the company to move to capture more business opportunities. As Apple's initial foray into the smartwatch market, most investors aren't nearly as certain about whether the Apple Watch will have the same success as the company's other mobile devices, as anxiety about just how broad-based the Apple Watch's functionality will be to mainstream users. Still, with many Apple customers jumping at the chance to widen their exposure to the company's ecosystem, some analysts predict that the Apple Watch launch could be even more successful than the iPad's initial launch several years ago.

Is there trouble ahead for Apple?
Ordinarily, a stock that had doubled in value would have most investors thinking about it being overvalued. But in Apple's case, the share-price surge reflects the level of pessimism that had been baked into the stock price in 2013. In the lull between major product releases, Apple appeared momentarily vulnerable, and the sell-off in its stock slashed half of its value and left share trading at ridiculously low multiples to trailing earnings. In the interim, all that's happened is that Apple has avoided the much-feared crash in sales and popularity, and now, the stock boasts a market-level multiple that still gives it room for further gains if investors believe Apple deserves a premium valuation due to its growth potential.

Source: Apple.

Some investors have longer-term worries about the sustainability of Apple's mobile-device series. Despite strong initial demand for the newest iPhone 6 models, concerns about whether Apple can keep coming up with enough improvements to force customers to buy new phones are only the latest sign of doubts about Apple's creative capacity after the death of Steve Jobs. Yet with hundreds of millions of iPhone users already plugged into the Apple ecosystem, there are good reasons to believe that they'll be reluctant to jump ship after having invested time and effort in building up their iPhone-specific expertise.

Even with the big gains in Apple, the stock's earnings multiple remains at levels consistent with the broader market, despite its arguably larger growth potential. Despite the company's huge size, Apple still has further expansion opportunities, both by spreading its geographical reach and by offering newer, innovative products to widen its offerings. Apple will see the health of the broader stock market affect its stock price to some extent, but for now, the strength of its business should help support Apple's shares through the holiday season and beyond.

Dan Caplinger owns shares of Apple. The Motley Fool recommends Apple. The Motley Fool owns shares of Apple. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.