The best advice I can give you is to decide on a fare that you are happy with...say $225 pp r/t. Then, when you see a fare that is $225 or below, grab it. I have played the waiting game, watching good fares come and go, only to be stuck with a higher fare than I wanted...thought that a better one would come along. I have also booked and then had a fare come along that was a bit better. But if it's only $50 or so, I don't sweat it.
I did book our Oct flights back in January. I'm waiting for JetBlue to open up for early Dec...then I'll book that trip.