Always break it down to manageable size. Whether that's one subject per day week or hour it's up to you. I usually do a good chunk of one course before I start another.
Ultimately it's up to you because it depends on your learning style. Some kids can stay with one thing all day others need a new activity every 30 minutes. Adults are the same. You're in charge of your studying do what you find works best for you.
Alex
