The gurus of the Manosphere are very facile in explaining things but not one (that I know of) has mentioned the Seven Year Itch.
This is from Wikipedia.
The seven-year itch is a psychological term that suggests that happiness in a relationship declines after around year seven of a marriage. The phrase originated as a name for irritating and contagious skin complaints of a long duration. Examples of reference may have included STD outbreaks that are known to significantly decrease in frequency after seven years, or mites that live under the skin (scabies) and cause severe itching that is hard to get rid of. Later on in the 19th and early 20th centuries it was viewed as an expression of imagined appropriate punishment for antisocial behavior, or as a simile for a situation with little hope in relief.
The phrase was first used to describe an inclination to become unfaithful after seven years of marriage in the play The Seven Year Itch by George Axelrod, and gained popularity following the 1955 film adaptation starring Marilyn Monroe and Tom Ewell.
The phrase has since expanded to indicate cycles of dissatisfaction not only in interpersonal relationships but in any situation such as working a full-time job or buying a house, where a decrease in happiness and satisfaction is often seen over long periods of time.
The seven-year itch can be analyzed quantitatively. Divorce rates show a trend in couples that, on average, divorce around seven years. Statistics show that there is a low risk of separation during the first months of marriage. After the "honeymoon" months, divorce rates start to increase. Most married couples experience a gradual decline in the quality of their marriage; in recent years around the fourth year of marriage. Around the seventh year, tensions rise to a point that couples either divorce or adapt to their partner.
In samples taken from the National Center for Health Statistics, there proves to be an average median duration of marriage across time. In 1922 the median duration of marriage that ended in divorce was 6.6 In 1974 the median duration was 7.5. In 1990 the median duration was 7.2. While these can fluctuate from year to year, the averages stay relatively close to the seven year mark.
Physiological aspects of love
The connection between the emotional and physiological aspects of love have been heavily studied. The parts of the brain responsible for the effects of love are the ventral tegmental area, hypothalamus, the nucleus accumbens, and numerous other parts of the brain. These parts of the brain create the side categories of love: sex, romance, and attachment.
Sexual lust for a partner comes from the hypothalamus. This controls the hormones in the body, which then create the physical responses (rapid breathing, accelerated heart rate) that are characteristic of a person in love.
Romance, or the idea of romance, is created by the ventral tegmental area, and the nucleus accumbens. These areas are filled with dopamine, a neurotransmitter. This, to the brain, is like a drug. Dopamine creates emotional responses, helping to control the pleasure centers of the brain. There are many other chemicals in the brain that help create this effect, as well as factoring in depression, and obsession.
The modern usage of the phrase gained popularity following the 1955 movie of the same name starring Marilyn Monroe. In the film, a man sends his family off on vacation for the summer while he stays back to work. He begins to fantasize about women that he previously had feelings for, when his new neighbor (Marilyn Monroe) moves in and he decides to try and seduce her. Things go awry and he ends up not going through with it, but he believes that his wife will somehow know that he is trying to be unfaithful.
Whilst the term was originally used for unfavourable conditions of a long duration, the movie helped to popularize its usage to refer to the decrease of romantic feelings between married couples over time. The phrase has become so popular that some couples use it as an indicator of the lifespan of their marriage, a famous example being a Bavarian politician Gabriele Pauli, who has been divorced twice. She suggests after seven years marriage should end, with the couple required to resay their vows if they wish to continue for another seven years.