LIke the article in LD In Depth says, "I do it, We do it, Y'all do it."
You demonstrate the behavior, do it together, and practice it a lot.
But specifically, I'd work at teaching the student to monitor that reading, so that s/he knew when it was time to break.
I think what you do in those breaks would be important - if they could be short, you could close your eyes and visualize the content, review it, and do other comprehension enhancing activities. If they need to be a bit longer, I'd read between washing dishes or fixing my bike -- X minutes in front of the book, X minutes (thinking about the reading) scrubbing.
Sue J, webmastress
www.resourceroom.net