Mostly TOEFL preparation takes 1-3 months for students with general aptitude.
But with students having a high aptitude, 4 hours a day in 1-2 months is enough time for practice, especially if the student belongs to an English school. As because of this, his /her English basics would be clear.
However, it will depend on what your goal is, or what your score needs to be. It could be anywhere from 2 weeks to 6 months.
Preparation time also depends on the:
Urgency of giving the test.
However there is no alternative of practice. Practice, practice, practice until you get a very high TOEFL score. There are various books and online programs that can help you to achieve this goal along with self – study, hard work and determination.