Mine is on a four-week cycle with an EP. With the farrier we had (very good at his job, but just couldn't fit everyone in and sadly we had to let him go) we were on a five-week cycle.
I would suggest you ask your foot-care professional how often your particular horse needs doing; and follow whatever advice they give you. IMO better to have a shorter cycle than a longer one.
Mine are done by a farrier, and they are done every six weeks in the winter and every four/five weeks in summer, this is basic, but it depends on the individual horse.