How many times a week should one have relations

Shalom uvrakha. It is a mitzvah to have relations on Shabbat, both because of the mitzvah of Oneg Shabbat and also because of additional kabbalistic considerations. The obligation of onah depends on a person's strength and on the amount of his work. The less he works during the week, the more he should increase in fulfilling the mitzvah of onah. However, he should not have less than one additional time each week, even if he is extremely busy. This is in addition to the obligation to have relations whenever a man sees that his wife desires it, and also during times of ovulation, relations should be had every day as long as the person has not fulfilled the mitzvah of pru u'rvu. 

With blessings, Benjamin Shmueli