Dear gordian_knot,

I am so sorry to hear about this. It must be terribly difficult to deal with.
I am almost too afraid to respond to this post because I feel like I am walking on egg shells and I don't want to offend by saying the wrong thing. I'll try...

I would like to start off by saying that I don't think it is right for someone to use Bipolar Disorder as an excuse to justify any behavior. People still know the difference between right and wrong. Choosing between right and wrong might be more difficult, but the option is still there.

It is very commendable of you to give your wife a second chance and wipe the slate clean. I don't think her affair and related behaviors occur because she isn't receiving the right kind of attention from you. I think she just craves additional attention in a new way. The idea of romantic attention from a stranger is quite appealing to some. This fills the void she feels. There are other ways to fill this void but this is what she has chosen thus far.

I know from meeting with Bipolar folks that this void can be filled with something to break the usual routine. It can be as simple as taking a weekly day trip to somewhere nice or as complicated as moving to another apartment or house. A change of job - if possible - can also be beneficial. Taking up a new hobby probably seems a bit tedious for someone in a mood episode, but if any kind of stabilization occurs - that is a good time to start. The idea is to change perspective.

I hope this information is useful to you.

To answer your question: No, I don't think this is uncommon. Even people that are satisfied with their mate may still crave additional attention to make them feel whole. Even though it seems to be the ultimate betrayal, you can preserve your relationship by working with your partner if that is something you are willing to do.

I know that many people would advise against ultimatums, but if a situation becomes too extreme sometimes one must choose between this or continued unhappiness.

I really do hope you find peace.