I think that as long as she is doing good in school, and doing her homework at night than an hour or so a night computer is fair. She is 17. If she was younger, then I would think less time was appropriate. She probably isn't going to get off the computer without somebody telling her that it is time. I have 45 younger siblings, and with all them they are more concerned with what they are doing then wathcing the time.....lol!!! I myself, won't be 23 until Apr. but I have 2 kids married and a house, so I am a firm beleiver in just b/c somebody is young, doesn't mean they are irresponsible, or always doing things to get them selves into trouble. If she is being responsible, and doing what she should be, then let her have about and hour a day. A computer can also be a good learning tool. I'd rather have my children (if they were 17) be at home on the computer where I could watch what they were doing, then at school on it, for a computer class, where I had no idea what they were doing. If you are concerned about sites she may be visiting, or inappropriate use of your computer, you can always set parental controls on it.....I hope this helps and good luck. Your niece is a very lucky person to have someone like you who will help out by taking her in!!!!!