Just like last year, Verizon and AT&T have reported second quarter results that impressed Wall Street. First, AT&T said Tuesday that added 2.3 million U.S. wireless subscribers while its phone customer defection, or churn, rate was a record low and its wireless profit margin was at a record high. Then Thursday morning, Verizon said it added 614,000 regular monthly customers while its phone customer churn rate also hit a record low.

As a result, AT&T’s shares shot up 5% Wednesday, the biggest upward move since 2009 according to Bloomberg, and added another 3% on Thursday. Verizon’s share gained 6% on Thursday after its results came out and the historical calculators will, no doubt, soon tell us that’s also the biggest one-day gain in quite a while. Investors who worried that competitors were closing the gap with Verizon’s network quality advantage were reassured by the subscriber gains even though the carrier may not have the best unlimited data plan prices.

But the wireless market’s languid competitive state in the second quarter is a regular, seasonal thing. With not much happening for shopping and no new iPhones to excite Apple (AAPL) fans, the three months from April through June are typically stable for the wireless carriers. And Sprint (S) and T-Mobile (TMUS) typically don’t go crazy with price cutting, since fewer potential switchers are in the market this time of year.

That all changes most years as we head into fall and holiday shopping season, not to mention the usual arrival of new iPhones in September, as some Wall Street analysts warned.

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“The recovery in [subscribers] is also partly due to record low churn across the industry in general, which we suspect will reverse later in the year with the new iPhone launch,” Jonathan Chaplin at New Street Research wrote after Verizon’s results came out. “T-Mobile in particular did not spend much to acquire subs this quarter (sensible given low turnover); we expect a more aggressive push from all carriers later in the year.”

For what it’s worth, Verizon (VZ) CFO Matt Ellis wasn’t willing to concede any problems ahead. “As we head forward, second quarter is typically seasonally the low quarter of churn,” he said on a call with analysts. “We’ll see if we get the normal seasonal uptick.” Verizon’s unlimited plan will remain a strong draw for customers, Ellis added later, saying that “absolutely I think that the trend on unlimited is sustainable.”

One thing is different this year from 2016, which longtime analyst Craig Moffett noted. Last year, AT&T (T) and Verizon were among the best-performing stocks and the further gains on their 2016 second quarter results pushed them into crazy-high territory for usually low-volatility big phone stocks.

This year, amid fears that unlimited plans were killing the industry’s finances, AT&T and Verizon’s stocks have been major underperformers. Through Tuesday’s close, AT&T was down 15% and Verizon had lost 18% versus the 11% gain in the Standard & Poor’s 500 Index.

“That today’s results will almost certainly be viewed as ‘very good’ says more about just how bearish sentiment has become in U.S. wireless than it does about the business itself,” Moffett wrote. “But it is precisely this uniformly bearish sentiment that has underpinned our Buy recommendation on Verizon. Investors don’t need things to get better… at these valuations, it is enough to see them stop getting worse.”