I turned up to the gate at ICN for a CX flight departing 5 hours earlier than the one I was booked on. I hadn't checked in, had bags tagged on the later flight, held no status and was travelling on a partner redemption in Business. The lady was happy to oblige with no mention of change fees and I departed on the earlier flight.

Sitting in the Arrivals at HKG, my phone starting receiving CX notifications stating that the flight I was originally booked on was delayed 3hr 5mins! That lovely gate agent saved me 8 hours of pure airport boredom!!!!

Good luck!