When our kids were younger we placed time limits on certain activities, like games. Over time they all learned to become self-regulating and balance their responsibilities. It’s expected that school work and household duties get done and there is time made for physical activity too. We trust them to manage their own time because they have proven the ability to do so. We would obviously step in and make adjustments if there were problems, though.
I think we sometimes make the mistake of thinking of computers like televisions because people stare at the screen. Sure, computers can be used for mindless activities but there are so many pursuits that are more interactive and useful.
Compare this with other activities. If we have a child into gardening, sewing, woodworking, or auto mechanics we don’t often limit the time spent on those pursuits unless they get out of hand. Maybe it’s easier to see things like that as useful because the need for those skills has been around longer. If you’re not technically minded yourself it might be more difficult to see the value of technology tools and pursuits.
You can also compare it to how we all ramp up for big projects and do what it takes to get them done. For example, some of us have large gardens where we bring in a big harvest and spend all day canning. We would never say “I’m sorry, your hour of canning time is over so you’ll have to stop and do some more tomorrow.” Or how about “Your lawn mowing time is up so you’ll have to come in now.” 
We see those as necessary life skills. Some technology skills can be that way too.
At our house, we pretty much encourage activities that build critical thinking, have home or career use, or can be used to bless others. Sometimes those pursuits require many hours in front of a computer. We don’t have a problem with as long as it doesn’t create problems with attitudes or isolation, etc.
I’ve also encouraged our kids to work on their own business ideas or volunteer to help others. I meet with them regularly to give guidance in those areas. Many of their pursuits make use of the technical skills they’ve learned in some way.
Every child and family is different so our specific choices might be different from those that work for you. But I think most of us want to teach our children to be self-educating, self-regulating, pleasant and responsible adults with the life skills to run their own households and who can contribute to society and bless others. So I’d say to keep that in mind as you make choices and help your children learn to find a good balance.
