I met with the folks at Wizard Labs last month when I got my first order of equipment. Since I was at the facility and didn't order prior to going in I had to get my nicotine in what they call an "orphan" (they don't pre-mix nicotine until you order it, if someone makes an order and they prepare, then the person ordering changes their mind they keep the nicotine in a special area for future orders, hence the notice on their site that it takes 3-5 days to prepare an order for nicotine). The only orphan they had that day was a 500ml bottle of 100mg nicotine. I purchased it and John, the owner, told me to transfer into glass bottles for longer term storage. They are very comfortable with short term storage in the plastic bottles they ship in, but in my case, that much nicotine will last me for a couple of years or more. He recommended transferring it to glass bottles (120ml bottles), putting them inside a plastic baggy and freezing until needed. I currently have three 120ml glass bottles in the freezer and am using what's left in the original plastic bottle.
I thought it was a good idea to go with the method recommended by the guy that makes and sells the stuff... BTW: great folks to deal with there...