Video Games and Children

I have a growing concern about video game playing that I am curious to get your opinion on. My children, just like when I was young, are interested in computer games, video games and anything to do with the screen. They don't have the latest and greatest and I refuse to get them an xbox 360, but they do have simple educational games that I let them play on the computer. The concern is more in the form of a question. What do you think is too much time even if it is educational?

I have allowed my son to play in half hour increments. If he plays a half hour in the morning, on the weekends, then that's it. He can't play anymore that day. Sometimes I allow him to play for a whole hour, but that is rare. I personally feel it is wrong to allow the kids to play in front of a computer or TV screen for longer than that. Although they are challenged, I think it is stunting their imaginary powers. It is harder for them to appreciate what it means to imagine on their own without any help.

Maybe I'm wrong. Maybe I'm blowing things out of proportion, but I've seen how addicting video games can be and I don't want my kids to grow up into big kids. I want them to be well rounded adults. What do you think?