$929. That’s how much the average family is going to be spending on Christmas presents this year (according to a survey by the the American Research Group). Much of that money will be spent on mobile devices like tablets, iPhones, and more. You might be a parent buying one of these things. Have you figured out how long you’re going to let your child be on these devices? Let’s face it—it can be addicting. According to the American Academy of Pediatrics, here’s how long your child should spend on a mobile device. 18 months and under: no time, unless it's video chatting. 18-24 months: limited use with you. 2-5 years: an hour a day. 6 and older: two hours a day. Make sure you have media-free zones, too, like dinner and bedtime. And lead by example.