The time taken to change page is too short when you're trying to read it, and too long when you're waiting for the page you want...
Simple answer: use bigger screens so you can get more on. I remember the old departure boards at Paddington where they had a different piece of wood with a poster stuck to it for each possible service and slotted the appropriate one into a post at the end of the platform. They were nice and big. You couldn't get screens that big when they first started using monitors, but they are all over the place now.