Airlines are in buisness to make the most money for their shareholders, not to provide the cheapest fares to their passengers.
For long haul, the pattern seems to be announce a (quite high) standard price a year before departure. Then there are various 'sales' throughout the year where things are discounted - Black Friday, Boxing Day, Goor Friday etc. With about a month to go before the flights they review bookings, and start discounting seats on flights with poor sales.
Last year I wanted flights to the US. They were about £2K 3 months before, but with a month to go they had dropped to less then £1K. Basically, I decide on a price I'm happy with, and if/when the flights drop to that level book it. More often than not its 2-4 weeks before departure. Weekends are often more expensive than weekdays in economy, but in PE, Buisness and First that's not always the case.
I'm being bombarded with EJ and Ryanair sales offers at the moment!