J.G.
We dont' really limit computer. Screen time is first thing in the morning before breakfast. Sometimes this means 15 minutes, sometimes over an hour. it all depends on when we eat.
But I'm weird, I don't 'see anything wrong with computer or TV time. Books are great, but so are computer games and certain TV shows.
I'm not worried. I gave my kids their big box of books for their "curriculum" (I homeschool and only buy them books and games, no curriculum), and my oldest literally danced around for 15 minutes with joy because of all the science books.
Everything has it's place, and limits are only to make sure things don't get out of hand.