In brief, a woman's sexual libido is strongly linked to the emotional part of her brain. A man's sexually interest is less tied to his emotions. This difference can create a great deal of sexual tension between husbands and wives, but it's really just a biological distinction between the genders. One of the things that is the same between men and women is that we are both affected by hormonally induced cycles. Most women have a cycle of 28 days which affects their mood, their desire for sex, and the release of bodily fluids.
Men also have a biological cycle, but it is of shorter length.
Males have a 3 day build up of testosterone. Men experience mood swings, changes in sexual desire, and a need for release based on this build up of testosterone. This means that the average male has a biological drive to be physically intimate with his wife every three days. None of this is meant to suggest an excuse for immorality or demandingness on the part of a husband. But a wise woman will realize that her husband is influenced by his God-given biology.