Originally Posted by
NZbutterfly
I suspect no one wants the middle seat so I'd advise checking in purely for that reason. Even if on a short hop I get irritated not being by the window. You could change in the lounge but thats pretty late if a main trunk route and full flight!
You don't need to check in though to select a seat. I often change my flights from the app and the first thing I do is seat select to get a new seat.