Olive Oil is fresh juice that is simply derived from squeezing the fruit...
When olive oil is exposed to oxygen, light, and heat, it is subject to oxidation, therefore proper storage is essential. As soon as you open a bottle of oil, the oxidation process accelerates and the oil will degrade fairly rapidly, we recommend that you treat your opened bottle of Olive Oil as you would do fresh Orange Juice, try and use it within 3 weeks from opening it.
Make sure you keep your oil in a closed bottle, in a dark container or closet, away from sources of heat like your stove. You do not have to refrigerate it, although refrigeration will not hurt the oil.