It is very possible that the memories being recalled by a particular person may just be a product of his or her imagination, and is not necessarily "real".
One way to identify the accuracy of a past memory, whether recalled spontaneously or under hypnosis, is by checking if the emotions evoked by the particular experience is more powerful than those evoked by a novel or a movie. When a person finds a particular experience of the past as more powerful than anything evoked by present life experience, it is possible that a past life memory is accurate. Although hardly scientific, this method is often used as a measure of the memory's validity.
Proving whether PLRH is an effective means of therapy or not is very difficult to answer. But one major concern in that field however, is that most PLRH therapists only have very little formal training. In that alone breeds a serious problem. Hypnotherapy itself is very difficult to master, how much more PLRH when it is a more specific specialty. So if you judge past life regression hypnosis based on the quality of training that its practitioners really get, it will be equal to mere quackery by any modern