Book as soon as you find a price that you like, if you know your dates. Sometimes when I've not booked airfare, I will book several reservations if the price is right with different arrival times, but what flight I MIGHT be on....but that's only if the price is excellent. Rental prices have not been very good lately and we are hoping that it changes. My August rate is pretty low as I got in one morning when the rate dropped, but then went back up by the afternoon....so no room for hesitation. My Oct rate is not great, so I watch for that one constantly. I've not attempted to look for anything for our February trip yet.