There is no correct answer to this question. Everyone's body, tension levels, and problem areas are different.
Also depends on your needs, budget and overall stress levels. For someone with more chronic problems it may be more frequent like once a week , or even every other day until you are feeling better and then a once a month maintenance thereafter. Receiving a massage at least once a month will maintain the work that has been done by your massage therapist.
Try not to stretch your sessions out to far because the muscles will have tendency to revert to their old patterns and you will have to restart over again. Ask your massage therapist how your muscles are responding to treatment so u can plan how often you may need to come back.