At least 21 days you should continuously listen to selective sessions during day and night but if you do not feel any changes then keep listening for 90 days, actively and passively, and after that you can listen again if necessary.
If you do not feel any changes after 21 days, do not worry at all. Give yourself some more time. Everyone has different reaction to subliminal messages. Therefore, do not be stressful about that and give time to yourself.
Try to enjoy this process as much as possible and be aware of absorption of adoptive messages by your subconscious.
However, you can listen to a magnitude of subliminal messages that makes you feel good and there is no time limitation.
All of the subliminal messages on this site are proved by scientific researches all over the world and they have been shown to be powerful and successful and they have made great changes in people lives. If you do not feel any changes, it could be because of a big resistance within you in front of changing or maybe you do not choose subliminal message precisely. In this case, you can use that session along with another method like visualization. Otherwise, choose another subliminal message to gain better results.