Cyber Monday will have its biggest year ever in 2015, but its importance is slowly diminishing and eventually, it’ll be a shadow of its former self.

Cyber Monday, the day after the Thanksgiving weekend when online retailers offer a blitz of deals, is set to grow this year. Adobe ADBE said last month that U.S. Cyber Monday sales will grow 12% from last year to more than $3 billion, more than ever before. Research firm eMarketer is similarly bullish on Cyber Monday, saying that sales could grow nearly 15%. In a study released earlier this month, professional services firm BDO revealed that 32% of chief marketing officers it surveyed believe Cyber Monday sales will increase this year.

While all of that may sound good for retailers, closer inspection reveals a softening underbelly for the year’s biggest online shopping day. Eventually, it may soon be eclipsed.

“[Cyber Monday has] been much bigger than Black Friday and Thanksgiving in the last few years, but it’s growing at a slower rate,” says Tyler White, a senior manager in Adobe’s digital index analyst team. “It probably won’t stay the top [online shopping] day for long.”

Yory Wurmser, retail analyst at eMarketer, says that by 2016, it’s possible that Thanksgiving or Black Friday will replace Cyber Monday as the biggest online shopping day of the year.

“There is a feeling that Thanksgiving Day is becoming a really important launch date for e-commerce,” Wurmser says. “It’s certainly rivaling the other days in terms of volume of sales. But I still think 2015 is a year early for Thanksgiving to surpass Cyber Monday in total sales.”

White wasn’t so sure 2016 would be the year Cyber Monday would lose its crown. He did, however, say that Cyber Monday will “eventually” lose its allure among shoppers.

There are a number of reasons Cyber Monday is being kicked from the summit. But experts agree the main issue is shifting online behaviors, prompting consumers and retailers to change their behavior.

“Technology—mobile in particular—has changed the face of retail, and has put consumers in the driver’s seat,” eBay ebay senior vice president Hal Lawton says. “While Cyber Monday is still relevant, at eBay we see consumers starting their shopping even earlier, with expectations for deals, promotions, and great prices throughout the holiday shopping season, not just on specific days.”

Meanwhile, retailers are seeing more value in getting customers to their marketplaces earlier in the season. According to Wurmser, retailers have discovered that the sooner they get consumers shopping the better. So they’re offering better deals earlier in the holiday shopping season to get people to spend more.

“Retailer behaviors are changing how consumers are shopping,” White says. He added that last year, “Black Friday was a bad offline shopping day but a great online shopping day, and that’s part of what has helped it catch up to Cyber Monday.”

All of the experts agree that the nature of online shopping during the critical holiday-shopping period is changing. While historically, people would kick off their holiday shopping on Black Friday, now retailers are offering deals earlier in the week or in some cases, earlier in the month. The National Retail Federation said that 57% of shoppers started in early November, up from 49% in 2008. The shopping season, in other words, has been extended, resulting in Cyber Monday losing some of its importance.

“What is clear it that the growth in online shopping as it relates to the holidays has changed how, when, where and why retailers offer their customers unique savings opportunities,” says Vicki Cantrell, senior vice president for the National Retail Federation. “Retailers have already given consumers several good reasons to not have to wait until Cyber Monday to start their holiday shopping.”

“We’re starting to see the effects of retailers making [deals] earlier,” White added.

Even PayPal PYPL , which processes online payments, is seeing a shift in holiday shopping. But unlike some companies, which believe holiday shopping starts in November, PayPal’s senior director of communications Anuj Nayar says it may actually start much sooner.

“PayPal data shows that the holiday shopping season now starts on Sept. 30, two months before Black Friday,” Nayar says.

A shift towards getting consumers to shop sooner has also affected Cyber Monday’s appeal to budget-conscious shoppers. Adobe’s analysis of the holiday season shows the best online deals are on Thanksgiving. The company predicted in October that Thanksgiving online discounts would average 26% off the regular retail price compared to 25% on Black Friday and 20% on Cyber Monday. WalletHub, a company that provides personal-finance advice to consumers, was similarly skeptical of the “deals” consumers are actually getting on Cyber Monday.

“Cyber Monday deals are not what they used to be,” says WalletHub analyst Jill Gonzalez. “Thirty-one percent of online items actually offer no savings at all.”

Looking ahead, Cyber Monday appears to be a tale of two extremes. Industry experts agree that Cyber Monday, in terms of total sales volume, is still the biggest e-commerce day of the year, and will likely generate billions of dollars for e-retailers for years to come. But its significance is waning, and, soon enough, it’ll be just another shopping day like many others.

“Cyber Monday will lose its spot as top online shopping day next year or the year after,” White predicts.

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