If your first priority is looking good in class discussions, then you should continue to brief each and every case in detail and review those briefs before class, in addition to highlighting your casebook and in addition to abstracting the holdings into your course outline after class.
If your first priority is doing well in the final exams, then you should skip the briefing and the pre-class brief reviews, and instead do your outlining before class and trust either your casebook highlighting or one of the "High Court Case Summaries" books to get you through class discussions. Then, take the extra time and either supplement your understanding with a commercial outline, or with one of the Examples and Explanations books.
I've so far only met one 2L or 3L who still briefs each and every case.
It isn't a matter of laziness: generally people are devoting all their waking hours to school anyway, so the only way to give more time to one method of study is to take it away from another.