The best treatment length depends on your treatment goals and complexity of your condition. However, a simple method to decide which treatment time is correct for you is as follows:
90 minute treatment: Full body massage, 2-3 areas of concern and compensatory/secondary  areas
60 minute treatment: Full body massage, 1-2 areas of concern and compensatory/secondary areas
45 minute treatment: 1 area of concern and compensatory/secondary areas
30 minute treatment: Focused treatment, usually one area addressed, no compensatory/secondary areas