To be honest you dont need to study at all. I didnt study at all and got a band 6 in science, rest around mid band 5s and 97 in computing skills.
People who studied throughout the year may have gotten mid 90s for each subject all band 6s etc. but the truth is we all go into year 11 the same...
EDIT: Just thought id mention, that to get marks similiar to mine or better without studying through the year you need to have a bit of natural ability, if you can get really good marks in your yearlies and half yearlies only studying when the exams are about to start then just do the same for the SC. But if you normally study a lot, then your going to have to keep doing that. Bassically keep doing what your doing now unless you feel you need to do better.