Originally Posted by
djk7
If the available seat is a middle standard economy seat, I'd wait. You have a chance of getting assigned an MCE seat at checkin. Even if none are showing now, upgraders are likely to come from those seats so that might be all they have to assign when the time comes. The downside is that there is a very slight possibility that not having a seat assignment could increase your chances of IDB if the flight is oversold.
If the current available seat is an aisle or window, then you might want to take it if you have a strong preference to avoid middles.
I agree with this. If you do wait, then try to check in at T-24 if at all possible to reduce the IDB risk as much as possible.
If you use any apps that allow seat alerts, then I would set one for aisles and windows and be prepared to grab one if it opens up before check-in. Upgrades sometimes free up seats during the last few days.