I don't know how old your kids are and if they play video games with friends, so maybe they're too young for this to begin with.
Do you give them some kind of additional time budget that they can manage themselves over a longer period? There are things that you can do on a screen that just take more time than one hour at once, especially when you're playing with friends (or even learning something by programming etc.).
Do you give them some kind of additional time budget that they can manage themselves over a longer period? There are things that you can do on a screen that just take more time than one hour at once, especially when you're playing with friends (or even learning something by programming etc.).