When you do the system fully the first four steps Prepare, Preview PhotoRead and Postview will take a total of 15 minutes for any book. Then you've hit a good time to take your break and allow mind probing.
Sakari, the problem the beginner faces is they too easily get pulled back into passive reading. That's why the limit of about 3 questions, trigger words and purpose. We don't want them spending more than 8 to 12 minutes in a postview . If they are struggling it means they need to come back out and check the purpose. Also by limiting the amount of time writing if they are still curious and want to know more by stopping before they are finished (sombunall) their mind will still be forming mind probing questions and leading them to spontaneous activation.
In the seminar we set the timer for them to help them get their reading done in the time they have available. Since the majority on the forum are self learning and often don't use a timer it's important to get them back on time another way and when you have 3 questions and about 15 trigger words, you've postviewed enough.
Once they become more experience and know what their purpose is activation flows there is no effort in forming questions so the question of how many questions should I write down doesn't come up. You just flow into the activation.
Alex
In other words once you're a proficient PhotoReader you just do it.