In general, the amount of tutoring your student receives should be based on four considerations.
Urgency of goals: If your student needs quick review and test strategies before she takes the SAT, every day for a week or two should be sufficient. On the other hand, skills such as reading and writing are usually best learned slowly, maybe once or twice a week.
Subject: Although reading and writing can be learned slowly, for rote memorization or concrete skills such as times tables or long division, daily or almost-daily practice is important.
Student age and interest: It is important to balance the demands of the subject matter with the ability of your student to keep up with them. Consider your student's enthusiasm toward tutoring, previous commitments, and their age. Every day is not too often for any student, if they are excited about the experience. If they are reluctant, however, too much time may turn them off even more.
Cost and availability: Many families do not have the resources to pay professional tutors for five hours or more a week. If this is the case, look for ways to support your student in between paid sessions, or through free tutoring services.