http://en.aegeanair.com/milesandbonu...ms-conditions/:
.If a Blue or Gold Member has not flown for at least once within a period of thirty six (36) months from the date of his/her last registered and Account-validated flight, then his/her Card and Account will be automatically inactivated and cannot be used for any purpose (mileage accrual or redemption) for a period of 12 months. During this period the Member may retroactively claim a flight he/she had made within the previous year so that to have his/her Card and Account reactivated. Otherwise, as soon as the 12-month period expires, the Card and the Account will be irrevocably canceled.
The fourth year (36+12) can be used to retro claim miles.