According to the sources I found, the likelyhood of affairs actually ending in marriage is between 3 and 5 percent. Of those marriages most fall into the 75 percent of second marriages that fail. Even though fewer than 25 percent of cheaters leave a marriage for an affair partner, most of those relationships are statistically unlikely to last. The percentage I recall is less than 10% actually make it. That percentage rose significantly if the affair couples had a previous romantic relationship together prior to their first marriage.
The reasons affair couple marriages primarily fail is described in the book: Private Lies: Infidelity and the Betrayal of Intimacy by Frank Pittman . Pittman identified several defects in the dynamics of affair marriages that span the scope of the relationship, from forbidden romance through established marriage and finally through breakup.
I'm paraphrasing Pittman, but here are some of those defects.
1. While still in their current marriage, the AP's become immersed in "stimulating unreality"; however the second marriage becomes reality. Only after the the divorce did things become real enough to see that their new marriage was a horrible mistake. They were too caught up in the infatuation to determine if what they were doing was sane.
2. The cheaters likely wrecked a family (or two) and inflicted a lot of pain on innocent people. Although they may have felt little guilt during the affair, after they became married, they were overwhelmed with guilt.
3. Divorces are a huge drain both financially and emotionally. After the AP's marry, they may feel a disparity in what had to be sacrificed to bring them together.
4. AP couples may believe that their new marriage will be as good as life during the affair. They believe that "the greater the sacrifices, the greater the expectations for the new marriage." In other words, “The more people enjoy the battles involved in wrecking and escaping marriages, the less they are likely to enjoy the business as usual of the new marriage."
5. Unfaithful AP's tend to develop a distrust of marriage and for the AP who is now a spouse. A relationship that started as lies, is not build on a trustful foundation.
6. During the affair and the divorce, the unfaithful couple isolate themselves, and live in their own private little world. Together, they feel protected from the devastation they have caused. In this situation, memories of the past or of the BS can be difficult. Later, when the AP couple try to reconnect with the people they hurt, they may not find everyone so forgiving as expected. They often find that they only have each other and they have become isolated from people they used to care about.
7. When the romance fades, as it almost always does in marriages, the AP's may not understand that this is a normal part of the growth of a marriage. They may discover that they do not have the skills to foster and nurture a deep and meaningful relationship. They usually believe that that they have just fallen out of love.
8. During the affair and the divorce, the affair couple will usually blame their failed marriage on their BS. In their mind, to believe anything else, now that they remarried, is a betrayal of the fantasy world they created to originally justify the affair.
9. The affair couple has an absence of a shared history together. It is usually this shared history together that creates a comforting familiarity to relationships. For an affair couple, talking about the past is difficult. An affair that destroys a first marriage makes it painful for both spouses to discuss the past and may cause jealousy and insecurity. AP's that marry do not want to discuss the good aspects of the past BS and previous marriage. They also do not want to hear about the "good times" the other partner had.
[This message edited by HardenMyHeart at 11:39 PM, May 2nd (Thursday)]