No video games?! That would be awful.
In all seriousness, I do agree with the boredom leading to imagination, but then again it only does so much, at least in my experience. When I'd get grounded from my precious Xbox/Live, and whatnot I wouldn't know what to do with myself, but I'd find little things and make them better due to creative thinking, but it only did so much. I can understand not letting them play 24/7 but only 30mins isn't that a little harsh?
How old are your kids anyways?
Not harsh, unless you believe that kids have a right to spend more time playing video games.
Instead, we interact with our kids one-on-one (or sometimes two-on-one), doing things that we consider far more important to the human experience than video games:
art, music, working out, soccer, baseball, reading, writing, math, swimming, reading stories, reading poetry, riding bikes/scooters, dance, martial arts, learning languages, meditation...
My kids are 8 and 5. The 8-year old would play video games all day if we allowed him. Instead he has won a prize for his art, which was published, and he has had a short story and a poem published. We never forced him to do these things - we give him dozens of choices (mostly, the things on the list above). He chose to work on art and writing. His creativity and skill got his creations published. If we allowed him free access to TV and video games, he would have lost his creativity and never gained any of the relevant creative skills.
Not that I don't see benefits to video games, or enjoy them. Just that the benefits of working on art, music, writing, sports, languages, etc. far outweigh the benefits of playing video games. IMO.