I'm trying this right now. I have a $137 ecredit that expires today. Just booked a 1 way to Seattle for $149 in Feb 2026.
Is best practice to cancel or keep it and simply change the flight? And if change, can I do a new destination? When I do book I'll need to add the return etc, at my expense.

Will see if get any insight here then try cancelling before midnight. If that simply puts the credit back then I'll book yet again and this time keep it and plan to change in the future.

Either way I'll report back here.