I recommend storing your tinctures in amber glass bottles, preferably labeled, and stored nice and neatly in a cabinet and out of the sun. Even though there are times I feel some tinctures need that sun energy emanating through them.
The reason I would not store in plastic is because the plastic could and most likely will leech all sorts of non-sense into your medicines. A lot of plastics leech pseudo-hormones that look like estrogen to the body. This can amount up to a major hormonal imbalance, especially that of aging males. That reason alone is enough to choose glass over plastic. Plus, glass just looks so much nicer :) There is something lifeless about plastic that I can't quite describe...?
Hope that helped!,
Dirt a.k.a. Danlyn Brennan
*Certified Clinical Herbalist*