Women's inclination towards serial monogamy does confuse men, especially beta males. A lot of men, especially beta males, will be with a woman 1-3 years and the sex will be frequent and good. That's still inside most women's serial monogamy zone. The man puts a ring on it, hoping to continue to get frequent access to vagina he deems acceptable or better for the forseeable future. There's something like a 6-12 month engagement, then the wedding, and then sex is still frequent for the first 2 years or so of the marriage. After ~2 years of marriage, the couple has been together for about 5 years, which is near the outer limits of women's desired serial monogamy window. I think the window is roughly 7 years long.
The median marriage that fails becomes a failure around the 7th anniversary, which is roughly 10 years of total relationship time. If you break down the 10 years, things are usually good for 5-7 of them (women's serial monogamy window) and then a couple will spend 3-5 years trying to make it work due to socialization/societal pressures before declaring it a failure.
After the serial monogamy window ends, this is how the relationship typically looks:
If the man is more alpha: The serial monogamy window is longer than shorter but will eventually end. When the window ends and the sexual frequency subsides, the man who has more alpha traits will have an affair because he has alpha traits desirable to women. The woman finds out and usually files for divorce. There are some occasions where she'll stay for some socialization based reason, but that seems to be less common than in the past.
If the man is a typical beta or a better than average beta: The woman will dead bedroom him. He'll get resentful. Things will be bad for him in most cases because he is much less likely to be able to cheat. If the woman has dignity, she'll file for divorce before she cheats but she might emotionally cheat or line things up so that she can monkey branch the second she files for divorce. Some women will have affairs and their men won't find out. I think women are better at concealing affairs. If the man finds out, he might file for divorce. She might file too. The occasional beta will agree to an open relationship or swinging arrangement, but this is less common than outright divorce. Some open relationship/swinger couples eventually divorce.
If the man is a lesser beta: He will look like a soy boy and she will routinely cuck him, often times openly. Many times the man will stay around for this.
