E-liquid storage is a hot topic among new and experienced vapers. Some argue that refrigeration is key to preserving liquid, while others will swear it is the source of the problem and that it causes the flavor to turn bad. Once thing that is generally agreed upon is that exposure to light and darkness is detrimental to the health and longevity of the e-juice. The truth is that storing the liquid in the refrigerator can degrade the quality and should only be done as a last resort or temporary solution.
The main reason refrigerating your e-liquid should be avoided is that the nicotine inside it is responsive to heat and light. Ideally, it should be kept in a slightly cool and dark area. The temperature in the fridge is far too low and will degrade the quality of the liquid. There are also usually artificial fridge lights that will interfere with the juice after being exposed. In order to avoid all of this, simply store it at room temperature in a dark area and keep away from all light.
Failing to properly store your e-liquid will lead to a rapid loss in flavor. It might even alter the flavor completely and leave you with something you cannot stand to vape, let only taste. Given the concentrated nature of the liquid, these solutions are particularly susceptible to temperature and light changes. Storing the e-juice in a cold place like the fridge often causes re-crystallization of flavors that come with a high amount of crystals already. This makes vaping difficult and often requires an entire new bottle.
It is also important to avoid storing in places like the fridge because a lot of bacteria festers there. Since water condenses in the head-space above the e-liquid, it is particularly attractive to bacteria. The low temperature of the refrigerator could also cause the liquid to begin clumping, which is difficult to deal with.
It is better to be safe than sorry. Storing your e-liquids outside of the fridge and in a cool, dark location will ensure you are going to have a good vaping experience. If for whatever reason you have to store it in the fridge, limit its exposure to the cold and artificial light as much as possible. Only put it in the fridge if you know you are going to be vaping it quickly afterward. But if maintaining high quality and clean e-liquid is a priority of yours, go ahead and steer clear of the fridge.