I am booked on UA869 this Tuesday flying BOS-SFO

I booked it fairly late, so got stuck with a middle seat. Been constantly checking the seats, and no aisle or window seats have opened up. I am 3P with United.

Did a dummy booking and it looks like there's at least 16 first class seats available.

Would it be best to check during the various upgrade windows, 120, 100, 72 and 48 hours before the flight to see if any seats have been freed up.

Any other strategies or advice in getting an aisle or window seat at this point