I have a EWR-YOW (stopover) - YFB - YOW (short layover) - EWR itinerary booked with Aeroplan, with the EWR-YOW legs on AC and the YOW-YFB legs on Canadian North. I've already flown to YFB and would like to postpone the return flight (originally scheduled for next week) to some undetermined future date. Is it possible to do a partial refund of 12.5K Aeroplan miles, or alternatively open-date the return flight? I'm aware I can change the return to some date far into the future and then change it again when I've decided on the return date, but I believe that will incur a change fee when I make the second change.