Welcome to FlyerTalk!

As one who flies this route, usually in F, the only thing I can say is that the number of miles required on a given date & class seems to correlate to the fare bucket availability and not the time to departure. The more seats available at the lowest fare basis the more likely the "saver" award level will be available as opposed to the higher mileage requirements. The exception I have noted is in First that always seems to be 80K miles each way.

One thing I would suggest is that when you initially search for awards and paid fares, do it for just one passenger, not two. If there is only one "saver" award available and you search for two it will not show one saver, one higher. It will just show two of the higher mileage awards. If this is the case, make one res at the "saver" award level and a second at the higher. Or, do the opposite and buy the cheap fare if available and use the mileage for higher award if there is only one cheap fare seat available, or the opposite. Check both mileage and paid fares for both one and two passengers and come up with the best overall value and use of miles. Good luck!