Past life regressions can be achieved with facilitation from a certified hypnotherapist through a number of avenues. One can set an intention for following a feeling or emotion into the past to see why it is such a strong one in this lifetime. One can investigate an issue in this lifetime to see where it appeared and how you handled it in another body, place, and time. One can move from a current situation into a past life spontaneously when the subconscious mind can see that answers to your questions lie there and not in the present lifetime. All of these and many others are options for regression.
Individuals may decide to do multiple regressions into the past. Depending on the intention, the need, the understanding, the client can visit different lives or even return to the same life that was previously visited.
Why would someone do more than one? If your reasons for doing regressions is to understand your reasons for being on a deeper soul level, experiencing your soul through the eyes of another body gives you the opportunity to look at life differently. Perhaps you have reincarnated as a male more than as a female, but in this lifetime you are female. What is it about your bucking the trend that is notable in the current lifetime? Or perhaps you have issues with weight now and wonder what happened in the past that is leading to the issue in the current life.
There are many reasons people have interest in past life regressions. We might want to know about people who we seem to have known forever, or we might feel that a place is so familiar that we must have been there before. Whatever the reason, it is possible to set the intention to find out more.
Human minds tell stories, so the living of another life through regression is another form of storytelling, except it is part of our soul's eternal story. And whether you believe the details or not, because your deep subconscious uncovered this story, it is a way to further understand a part of you that is usually outside the realm of your consciousness. I tell clients that it is a metaphor at the very least, and one can always learn from these stories and benefit from the additional insight.