Airfares question

[hdsqrl]

As I'm not much of a frequent-airline-ticket-buyer, are there historically better times of the year than others to book a flight for the week of Thanksgiving?  Or is it a buy-as-early-as-you-can kind of thing?  We're hoping to head to CA, and right now I'm seeing fares online ranging from the mid-$300's up through the mid-$400's.  Book now, or wait?

I need a crystal ball.  Thanks to anyone who can help!