That increase should have been seen as positive because Apple aims to become less dependent on selling iPhones and shift to selling its existing customers services like Apple Music or add-on devices like the Apple Watch or AirPods.

But analysts voiced skepticism. Apple’s best-selling product, the iPhone, has seen relatively flat unit sales over the same two-year period. On Apple’s earnings conference call, Bernstein analyst Toni Sacconaghi said that the combination of trends implies users are hanging on to their devices longer, and he asked Apple Chief Executive Officer Tim Cook whether investors should be worried about that.

Cook responded that it was up to investors to decide what to focus on, but said he was comfortable with customers buying used iPhones.

When customers sell their old iPhone for a new one, the old iPhone “winds up with another customer somewhere else that is perfectly fine with having a previously owned iPhone. And so I view all of that to be incredibly positive. It’s more people on iPhones, the better,” Cook said.

Laura Martin of Needham & Co pressed Cook on whether the larger device base meant more devices per user, or more users - an important question, because a user with both an iPad and iPhone is likely to only purchase one Apple Music subscription, for example.

Cook said “there are many, many, many more” Apple users than two years ago but declined to give an actual figure.

The signals on how well Apple is monetizing users were mixed. Sales of its “wearable” accessories - Beats headphones, AirPods and the Apple Watch - were up 70 percent year-over-year in the fiscal first quarter ended Dec. 30. But services revenue - which includes Apple Music, iCloud and the App Store - fell short of analysts’ expectations for the December quarter, at $8.4 billion, and was down slightly from the previous quarter.

Apple has yet to disclose plans for how it will distribute the television shows in which it has been investing in recent months, which could become a large business.

“They’ve been building up the services business for several years, knowing full well that at some point the gravy train on smart phones is going to end,” said Bob O‘Donnell, head of Technalysis Research.