I would say that regression therapy is useless. But it is just my opinion. I think, what once happened you never change. So what for a regression? What is important is present and future. Spiritual teachings argue that what you think so You create, therefore most meditations. But, if you realy want know what was in your past life, you could do meditation about too.
When people really want solve their problems, it could take a years of meditations. But, you do not must constantly sit in meditation. Try used sleep - the last thoughts before sleep.