As above, just keep an eye open for a promo.

Booking so far in advance - typically more than 6 months - can indicate to the airline that your trip has some certainty and rigidity about it and therefore can probably command a premium. Discretionary travel is mostly booked 6 months to 6 weeks before travel, and this is when the airline will be generally looking to attract people to fill seats, but leaving enough vacant for last-minute bookings. Once you get into the last 2 months, maybe 6 weeks, then prices may typically start to rise as you're a last minute booker and your travel is again time critical and can command a premium.

These are very generalised observations, not all airlines operate the same pricing model, and certain flights and booking periods will always be outliers from the general trends. For example a sports team making a booking for multiple seats on a specific flight can often upset the pricing algorithm as they eliminate a lot of the discretionary fare buckets.