Booking 6 months out will pretty much guarantee you are paying too much. The best flight prices are most commonly in the 30-90 day range. A great way to keep some eye on it far out is to use
https://www.google.com/flights You can search for your flight including specific times/non-stop/etc. Then toggle to "Track prices" and will alert you when they increase or decrease. I still haven't booked our April flights yet as I expect them to drop in another month or so.
If you're extremely worried about availability of flights you can check for available seats and how many more seats are available at that specific rate every week or so.