Well, first of all - be a little careful about psychiatric diagnoses for your spouse. The temptation is clear, and sometimes it's appropriate. However, when a WAS is in crisis, they often APPEAR to have a disorder (like Narcissism or Borderline Personality Disorder) but really don't.
How do you tell the difference? The spouse who really doesn't have a disorder usually wasn't this way before the affair, and will usually return to normal behavior in a few months or years once the affair is over.
The spouse with a true personality disorder, on the other hand, usually showed signs of it going way back into the past, even early in the R when things were "good".
Now - if your W has had multiple affairs over a three year span, that's suspicious. Was there anything in her behavior prior to those three years, or in her past relationships before you, to indicate a personality disorder? Are there any confounding variables, like substance abuse?
As for whether you should be trying to win her back? That's a tough one. When kids are involved it's usually worth being able to say you did your best to save the marriage. But when a spouse is a true, chronic, serial adulterer - you are putting your health at serious risk by continuing a physical R with them.
Perhaps the correct answer lies in detaching but leaving the door open in case your spouse actually pulls it together and does all the things that it would take to win you back: serious individual counseling, medications if indicated, demonstrating good faith by being celibate for a period of time, etc.
And of course, working on yourself and being the best you can be, learning from any mistakes you may have made in this R, is always the right way to go.
