Ron....that's gotta be the $64,000 question on this board! You'll get advice ranging from "buy now" to "wait until just before you leave." Personally, I start checking right away on comparative sites like kayak.com, and I input several different airports close by....in your case, Seattle, Bellingham, and even Portland. I usually check a couple of days a week to see if any deals pop up...if there's something in my comfort zone, I buy. If not, I usually start checking more frequently 6-7 months before departure. I also sign up for newsletters from all the airlines that fly from my home airports to my destinations, on the off-chance they may announce some sales. You might also want to consider alternate destinations like Shannon, or even Manchester or Glasgow, from which you can reach Dublin via discount airlines like Ryanair and Aer Lingus. London, too, might be worth consideration. While, in most cases, you'd have to change airports, you can get connections to Dublin from Heathrow thru Aer Lingus and BMI. Bottom line....it's a crapshoot.