It is usually the second week of January that the sale starts , I have booked for march , June and September 2018 in 2017 , I could have saved a few hundred euro if I waited but nobody really knows what the prices will be in the sale , If the flights are almost fully booked then the sale prices could be more expensive than if booked months in advance , If I am happy with the price at the time I will not risk losing out and purchase there and then, Nothing worse than having planned dates only to find no flights are available .