For maximum flavour and to ensure the longevity of your e-liquid, store in a cool, dark place. Keeping the bottles away from direct sunlight and heat. Likewise, don't go too cold. However for long-term storage some vapers store their e-liquids in the fridge.
Providing the bottle is stored correctly and the lid is tight, once opened the liquid can last up to two years.
Always keep the bottle sealed and away from children or pets.