How far ahead of time to book flights?

[OREOSpeedwagon]

I've found a flight on priceline.com to Dublin, Ireland for spring break for $503/ticket, but I'm not sure if we're ready to book the flight yet. How far in advance should I buy the tickets? Will new flights come available closer to spring break? Any help would be appreciated.

 

[Injury]

Sooner the better. Prices go up as it gets closer because tickets get in higher demand... then they crash way down in the week or so prior to ensure the seats are taken.

I don't have THAT much experience booking flights, but if the price goes down it may be possible to call and have it adjusted.