A new survey suggests Facebook fatigue may be setting in for some, especially among the younger users for whom it was initially created nearly a decade ago on the Harvard campus. More than a quarter (27%) of Facebook users plan to spend less time on the site this year, with 38% of those ages 18-29 planning to cut back, according to a new study by Pew Research Center’s Internet & American Life Project. This is the first time Pew has asked people about future Facebook use. While there is no base comparison, it seems to support the thinking that younger users, who often lead the way in social media consumption, are less enamored of Facebook than in the past. The Pew finding also echoes the results of an informal poll of six Facebook and Instagram users ages 17-28 last September by Macquarie Securities. In it, nearly all said they expected to be using Facebook less six months from the time of the survey. That report highlighted the growing popularity of Instagram, especially among teens. Still, the Pew study found the vast majority of Facebook users (69%) plan to spend as much time on the site this year as in 2012, and 3% expect to spend more. Users devote roughly seven hours a month on average to the site compared to only about two hours each to others, such as Google, Yahoo and YouTube. Maintaining that level of stickiness is key to Facebook’s ad model. The findings could give Facebook some cause for concern. For example, 28% of users say the social network has become less important to them than it was a year ago, and 34% say the amount of time they are spending on Facebook has decreased over the past year. Women are more likely than men to have increased time spent on Facebook, at 16% versus 9% for men. The results were based on a phone survey of 1,006 American adults conducted from Dec. 13 to Dec. 16, 2012. The margin of error for the whole sample is plus or minus 3.6 percentage points.