As a rule, herbs are not intended for long-term use. When being used for more than one month, herbs should be "pulsed" -- meaning they should be taken for cycles of ten to fifteen days with a three day to one week rest period between cycles. One common mistake made by new herb users is the "a little made me feel better, so a lot will make me feel great" theory. I strongly suggest you follow, and do not exceed, recommended doses. Also, if you are not working with a trained herbalist or naturopathic physician, DO YOUR HOMEWORK. There is lots of information on the market and on the web about herbs. Be responsible and realize that you should make sure you are knowledgeable about anything you put into your body. 

One of the things that used to overwhelm me when shopping for herbal and homeopathic products was the wide array of products intended to address the same symptoms; twelve products with similar ingredients, different packaging, and wildly differing prices. In speaking with people in the industry, I have learned that when ingredients are similar, it is the herbal company's marketing costs that drive the price up. So, with all other things remaining equal, pick products from the lower range of the price spectrum.