Let me start by saying that I was basically raised by a television from 3 to 12. Looking back, I don't think this damaged me all that much, but I wish that my parents demanded more of me in the form of reading or some other kind of creative activity. But hey, as a result, I grew a very healthy appetite for pop culture.
If I were a parent, I'd shoot for somewhere around 2 hours. 1 can be done, but probably wouldn't be likely unless you owned a whip... Also, If I'm being real here, the 17-year-old should probably be out chasing girls or socializing with friends instead of sitting in the house playing his video game console. 9-year-olds socialize with their friends through Mario and Zelda because they can't get a job or drive, but your older boy should be acting like an older kid.
If you're sick of hearing them whine, kick them the hell out of the house like my friend's mom did - I think back to those times and thank her style of parenting. We had a lot of good times in the back yard/neighborhood.