Met a family on the weekend who booked and paid for a DONE4 in Jan 2009 for travel at end of Feb 2009.

When the anniversary offer was announced they approached CX and and asked them to rebook them so they could claim the lower fare - they even changed the dates without changing the routing. CX refused and told them the only way forward was to cancel the original booking with the 5% penalty (and wait for refund) and then make a new booking at the cheaper fare.

I thought IATA rules were that any change to the 1st coupon meant that the fare had to be that at the date of the change, which in this case would have been the 10% discounted fare.