Frequently. I'd spend perhaps 10 minutes underlining the answers. You could do it without reading the questions.
One time, I hadn't studied and during the talk the PO asked if I could read the Watchtower as the assigned reader was absent. Even though I could read it as good as anyone else without pre-reading it I declined based on the fact my W. wasn't marked in ink. For my sin of not studying I was deleted (never officially told, but my name disappeared from the list) from the Watchtower reader list for nearly 2 years. I got the reader job back when they made me into an elder.
3rd