This depends on you as a person. Most clients come weekly or every other week. We will not work with someone less than that as doing so is not therapy but more coaching. Research shows that by the 6th to 8th session, clients either stay in therapy or drop out. We find that clients know by the 6th session whether therapy will be of help to them or not.
My recommendation is to give therapy at least 6 months. You can go longer or shorter and it depends on your issues and how much work you want to put into yourself.