Unfortunately there is no correct answer to this question. Each person is different, and thus an individual's rate of healing is also different. It may take one person only three days to walk one hundred feet after knee surgery, however a patient who had surgery on the same day may need five days to reach the same distance. This is due to the variation in pain perception, motivation, and healing rate we each have.
Rather than setting a date to complete therapy by, set various goals that you would like to achieve during your rehabilitation program. Make this your focus, not time. Reward yourself for achieving these goals, regardless of the time taken to reach them.
A quick tip on reducing the amount of time spent in therapy is through performance of a home exercise program. Although the physical therapist works with the patient during therapy sessions, it is important for the patient to take an active role in their therapy program. Daily participation in a home exercise program is a major factor in how quickly one recovers.