Based on people's experiences, how long does it normally take for QF to refund, in this case, a full J class fare to LHR if one has to cancel prior to departure and it was paid via credit card?

Also, having never flown paid J class before, I presume that someone could potentially no show on the outbound sector, then make changes to the booking to transfer the outbound sector to another date and then possibly cancel the booking if need be and be entitled to a full refund?