If there was any shadow of a doubt that the smartphone industry is slowing, recent updates from Apple (AAPL - Get Report) and Samsung (SSNLF) was a reminder to investors that phones aren't flying off the shelves like they used to.

In recent weeks, the two smartphone makers have delivered bad sales news, with Apple slashing its revenue guidance based on weak sales in China and Samsung also issuing lackluster revenue guidance, citing a "stagnant and fiercely competitive smartphone market."

There are multiple reasons for the slowdown in smartphone sales: One important one, according to NPD analyst Brad Akyuz, is that phones have just gotten much more durable.

"The devices are so much better: Components are getting better and better, batteries are getting larger," he explained. "Storage was also an issue several years ago, but that motivation disappeared with cloud storage."

In fact, at least one phone maker -- Huawei, now the second best-selling smartphone maker in the world behind Samsung, and ahead of Apple -- has taken to boasting about long its new phones will last. At the October 2018 unveiling of its top-of-the-line Mate 20 Pro, Huawei enlisted a German firm that simulates smartphone use to show that after 18 months, the phone's performance only degrades by 5% -- openly encouraging the idea that customers can and should go years and years without upgrading.

Huawei certainly isn't alone in shifting its messaging around the slowdown in smartphone sales. For its part, Apple has highlighted the average selling price of its iPhones as unit sales have plateaued, and as iPhone prices have gone up dramatically in recent years. The iPhone 6 and 6 Plus, Apple's best-selling generation ever, started at $650 for an unlocked version, whereas an iPhone XS starts at $1,000.

CFRA's Angelo Zino said that investors can expect a "no growth" environment for iPhones throughout 2019 and most of 2020. But, he noted, sales could stir back to life with the introduction of 5G-enabled phones in late 2020, when 5G networks are expected to be more widely available in the U.S.

"We continue to expect a decline in smartphone units in 2019, we think we'll see some stabilization to modest growth in 2020, partly driven by the availability of 5G in the U.S. and China," he said. "When you look at 5G and how it ramps, it won't have any impact on the smartphone market until 2020. I think it's a good thing that Apple is holding off on rolling out a 5G device, since they wouldn't get the bang for their buck until then."

In the meantime, Apple is more aggressively touting its services segment. In an interview with Jim Cramer on Tuesday night, Apple CEO Tim Cook teased more services offerings arriving in 2019, even hinting that they may be in the area of health care. "I do think looking back, in the future, you will answer that question, Apple's most-important contribution to mankind has been in health," he told Cramer.

Apple has also opened up some of those services on more platforms, beginning to break down its famous "walled garden" product ecosystem, for example entering into a partnership with Samsung to deliver iTunes on Samsung televisions.

"What Apple is doing right now with their services push is bringing the walls down and allowing services to run on multiple ecosystems, and that indicates that they have to bank on these services going forward," Akyuz said.

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