Some of this is mine, some I borrowed... I have 100mg/100% VG-nic in well-sealed amber glass bottles in the freezer. In plastic, especially LDPE, it will oxidize, even in the freezer. I’ve heard, some PG-nics in glass do oxidize in the freezer after about a year. I don't have any information on frozen ready-to-vape e-liquids with flavors, since I make my own fresh as I need them. I don't buy flavored e-liquids, and I only freeze unflavored VG-nic. If you feel better by purging the headspace of the bottle you filled (air space) with N2 (nitrogen gas) or Ar (argon gas) to rid it of O2 (oxygen), ok. However, I think it’s a negligible effect. 3 mL of headspace air at 25% O2 will give enough O2 to, at most, react with about 5 mg of nicotine. And that is only if it all reacts. VG naturally contains about 2 mg of O2 per liter, which if it all reacts will oxidize about 0.38 mg of nic...per liter of VG. If the nic started out colorless before freezing, and it remains colorless, it has not oxidized. Nic-oxides are deep brown colored, and it takes barely any at all to yellow a nic solution. It takes considerable coloration before the original nic concentration is significantly impacted...although you may detect a tobacco taste and added TH. Testing is fine if you want to do that, but no color change means no oxidation. And kit titrations are really only accurate to about +/- 10%. 10% oxidation will be a very deep orange-brown. Cold slows all reactions down, frozen solid or not (VG does not freeze entirely). This is a function of chemical kinetics and molecular dynamics...nic and O2 cannot move well in the thick glue-like liquid that VG turns into in at freezer temps, so they don't find each other as easily. And since the only real source of O2 that can impact nic is from the external environment, well-sealed glass takes care of that. Plastics tend to be rather “O2-porous”. Yes, very cold VG will absorb water from the air, but again, this is a negligible effect. VG is too thick to syringe or work with very cold, anyway, so allowing it warm to room temp before opening is normal. Making diluted unflavored nic with added water will introduce more O2, but probably very little. Viscosity is lower, however, so nic cycles to the surface more often...but again, if it is sealed in glass, I doubt the effect after a long time in the freezer will be noticeable. I don't have any concrete data on this. Cold VG will expand when warmed, so I advocate a few mL of headspace. Let the bottle warm standing up...that air bubble will expand more than VG and can cause leaking under the cap if the bottle is on its side and in a warm environment. I use Specialty Bottle - Wholesale Glass Bottles, Jars, Metal Tins and Plastic Containers 100 mL Eurodropper amber bottles. This is a company that makes glass for chemicals, so it is not cheap glass with many defects that can crack with temp change. I've never had a break, but I'm not saying it is impossible. Glass is glass. REMEMBER!!! SAFETY IS PARAMOUNT WHEN USING ANY STRENGTH NICOTINE!! When I was filling the 100ml bottles, even though I was using a 1 gallon pump, pumping into a funnel which was in the bottle, I still wore nitrate gloves and I was glad I did. The first “squirt” of the pump had enough force to send a couple drops of nic onto my glove. I was even washing the gloves I was wearing or, I just changed them. Look closely how I’m holding the funnel in the bottle. I’m, actually, holding the funnel up a bit as to create an air gap for air in the bottle to displace. Liquid goes in and the air has to go somewhere. The dropper insert (the little plastic bottle insert) protects against spilling and allows syringe access to the liquid. Others use glass bottles with cone-caps for good sealing. Specialty Bottle has blue and green glass as well. Dark is good, but it is UV that catalyzes oxidation most, not so much visible light, and freezers are dark. Once you’re done, you’ll have enough nic to last quite a while. I have read where some people have had VG-nic in their freezer for 4-7 years with no color change and no loss of nic strength. Some believe VG-nic will last essentially forever unchanged in the freezer and in glass. The comments in this post are the views of the author and others. DIY and store nicotine at your own risk.