Limiting kids’ time with electronic entertainment

Right now, I’m looking for tips on limiting my 9 and 5 year old boys’ electronic entertainment time.

So far, the right answer seems to be combining TV, video games, and internet  into one lump time segment per day, but I’m open to other ideas. 

Personally, I can understand the desire by kids to play video games all day, preferably with a big bowl of candy next to them. In fact, playing PC games were how I cut my teeth in the computer industry. 

That led to opening a retail computer & software  store, so I know that it’s NOT all bad. I believe there’s valuable knowledge to be gained on the internet, using a computer, and even, if properly used, (gasp!) television.

However, what’s a fair amount of time per day?