Unlike wine, olive oil does not age well.  As a rule, olive oil will be good for 24 months from the date of harvest. However, once the bottle is opened, it is recommended to use the olive oil within 6 to 8 months to maximise flavour and ensure that it will keep all its properties.
At first, the olive oil will be bitter and spicy, characteristic of the olive at the beginning of the season (high level of antioxidants).  With time, it will reveal the flavour and taste of its olive variety and origins.