I don't have a limit. For me, it's a general sense of balance. Some days they play games on the playstation for 5 hours. Other days 30 minutes. In general, my kids use Media for about 30 minutes in the morning, and then for another 2-3 hours during the course of the day. But my kids have their own computers, tablets, and then a playstation. They go back and forth with what they are really interested in using, and some days they walk off with my iPhone and pad because what they want isn't on their androids. But we are a technology house. Let me say that again, it's technology, not junk. Some avid gamers-like my hubby- grow up to make lots of money. Research shows that kids are gaining in IQ because of the skills they are picking up from, get this, video games!
My toddler probably does a few hours a day too.
In my opinion, media is no less valuable than any other activity. Why is drawing better than playing minecraft? Minecraft requires problem solving, fine motor skills, team work-collaboration, negotiating conflict-, and reading. My kids are also learning a lot of social science in the process too. They can tell you what a Golem is, for instance. In many ways, it teaches more applicable skills than most non-media activities. There are some great shows on netflix. My kids know lots of interesting stuff about animals from watching wild kratts all the time. And I swear my oldest read fluently at 4 because she spent all of 3 watching super why and word world.
My toddler has been watching utube videos of Just Dance. She is trying so hard to dance. It's cute as hell. I see nothing wrong with it. Soon she will move on to her next interest. But to do this, at 22 months, she figured out how to turn on the computer-it's a touch screen-access the browser, and then call up its history to get where she wanted. It's amazing to watch.
I should add that we homeschool, so we have tons of time in the course of a day for lots of things. My oldest also usually reads for two hours and crafts for another hour, and we are out of the house from 1-3 hours every day. We have the luxury of time...