This detailed story is being presented as it was posted on a listserv, with permission to post here.
My wife and I have had many lives together. One explanation for this is that two people develop karma that is best overcome by that very person you developed the karma with. I'll elaborate with an example (actual story of my wife and I):
I regressed my wife because she was experiencing an extremely difficult pregnancy. We figured we would try anything to stop the sickness and pain upon asking her higher self to take her to a time and place that would best help, she began sobbing quietly. She was begging me not to leave for the new world (1700's), and I was promising her that I would return.
There were several serious issues with us: she was my maid, I was married, and (I learned later as she screamed at me while boarding the boat) she was having my child. During these times, a baby out of wedlock meant social ruin, and I was leaving her. I told her I was going to return in a few months and bring her back with me once I find residence and a job.
Well, I didn't return for reasons unknown. She was banished from the house, ultimately from the entire town, and was left without food or shelter. When I told her to go to the next significant event, as a therapist I almost had to take her out to her safe place. She was in extreme pain, out on the docks with one last hope of my return, delivering her baby all by herself. It became worse; our love-child was stillborn causing her deep emotional pain (imagine trying to explain to people outside of my office that the shouting and crying was perfectly ok), and as a result of no help, she bled to death.
Yes, very sad. But this helped her through the remainder of the pregnancy. however, because of the deep emotional/physical pain associated with childbirth and me, she continued to have fear and reservations during the birth of my (current) son. (It was later learned that she either lost or had taken away several other children at birth. We have yet to discover the source of this karma of childbirth.)
So, to answer the initial question, "How do you feel about his theory that we often choose the same partner over and over?" it can be seen that my wife and I developed karma together that can be resolved in just one lifetime, as opposed to several because maybe in one life her partner left her not to return, but didn't have a child together, which would require yet another experience of losing a child. By incarnating together as we did, we are able to finally balance out the karma of us being separated, of she having a horrible childbirth experience with my child, of her being accepted in society as my wife, and others maybe.