The best way to store weed is by using glass jars, metal coffee tins, or tupperware. If the buds are too dry for your liking then sprinkle a couple drops of water overthe buds and closes the container. Place it in a cool, dark place. Remove the lid from the container daily and turn the buds, allowing carbon dioxide to escape. And so they don't mold.
But then again , that's storage for more extended periods of time really, I don't think you'll be keeping your 1.5g long enough ,no?
About the potency over time question.
Potency over time will not decrease if you store the weed properly. It maintains it just fine.
Marijuana buds are covered in little microscopic hair thingies called trichomes. (other plants have them too, just with no THC in them)
Long story but to some it up, THC is made in those little trichomes.
Every time you touch the buds of a growing or dried bud you can damage these trichomes and they eventually rub off. So yes, improperly stored and abused buds will loose potency over time. Frezing the buds will also cause the trichome stalks to break off.
The 'real' way to determine if a pot plant is ripe is to look at the trichomes. It takes 50-100x magnification to see them. Then trichomes go from that translucent color in the pics to an amber color when totally ripe.