Four hours, every day?! What a horrible expenditure of time!
I've never found the whole 'short bursts' thing to work, i prefer, and it worked for my A levels at least, working on each subject in long extended chunks, as you do. But then i only ever really did that for revision coming up to exams anyway.
But the amount of time i spent on a subject really depended on how much i needed to know ready for the exam, i certainly didn't spend the same time on all my subjects.