I've been able to change seat assignments within 24 hours-- the seap maps seem to close out only a few hours before departure. Has your experience been different?
Yes - I've had to go through back through OLCI to change seats - I often do this 5-10 times as better seats become available inside 24 hrs. It's possible that you can change seats through the reservations page inside 24 hours if you're not checked in; I haven't tried that.