There is no one-size-fits-all answer to this question, as the frequency of sex that is healthy and satisfying for a couple can vary depending on a variety of factors, such as age, health status, and personal preferences. In general, it is important for a couple to communicate openly about their sexual desires and needs, and to strive for a frequency of sexual activity that feels comfortable and enjoyable for both partners.
According to a 2017 study published in the Archives of Sexual Behavior, the average frequency of sexual activity among couples in the United States is about once a week. However, this frequency can vary widely, and what is considered "normal" or healthy for one couple may not be the same for another.
It's important to note that quality of sexual activity is more important than quantity. Consensual, satisfying, and communicative sexual experiences can be beneficial for couples regardless of the frequency. If one partner is experiencing a decreased desire for sex, it's important to talk openly with each other about it and seek professional help if needed.