Till Affinity returns to share her experience, my thoughts'd be first to ask the ones doing it why not longer or if they are planning on increasing once they are sure you tolerate the short time. I'd think the frequency'd need to be 1-2x/wk and similar to acupuncture you should be noticing improvement after 5 sessions, but I'd ask them that too, because praps the short time and then increasing needs to be taken into account.
Because it's not really acupuncture, but often compared, my experience with acupuncture in short is that "too much" (needles, length, frequency) can be counter-productive and that it's important for the people who do it to be well-trained (in the case of acupuncture best Chinese-trained).