Originally Posted by canadiancow

I think the spirit of that term is that if the flight is J0 Y0, you can't just swap the eUp to a comp up and get your credits back. There needs to be space for sale in Y to downgrade (or rebook), and there needs to space for sale in J to do the upgrade again.

I generally only do the downgrade/upgrade route when I'm booked in a promotion window (like bonus Aeroplan miles for bookings between dates X and Y). Otherwise, if space is available on the flight, it is much faster and easier to cancel it online yourself and make a new booking.