We do not have enough data on this route to provide a reliable graph showing how many days before departure it is the best to book.
However, usually the closer it is to the departure, the more expensive the tickets are.
The cheapest flights you can book on the route Vilnius Airport (VNO) - Cote d'Azur (NCE).
There is no direct flight on the route from Vilnius to Nice
Il volo con scalo più breve dura 5h 10min.