Because each woman's cycling pattern is just a little different, and each cycle is unique, there is no hard and fast rule about the amount of abstinence. For a woman who has typical cycling, the average number of days of fertility is about 9-12, at least for beginners. It is important to keep in mind that studies have consistently shown that couples using NFP to plan their family have as many (or more!) acts of marital relations during a cycle as other couples, it is just distributed differently.