I am 21 and growing up my parents also limited my siblings and I's computer time. They'd go as far as hiding the mouse or the power cords. I don't blame them BUT at the time (14-18) I used the computer to experiment with programming and it seems like my peers who did the same but had "unlimited" access to a computer had a great headstart.
So I think the time kids spend on the computer should factor in what they use it for. I'd secretly monitor their activity to determine that.