I have two reward tickets booked with Qantas on different dates and am still deciding which one to use. In the meantime, Qantas has sent me an email about a slight change in the flight time which in one way is great, because it gives me the opportunity to cancel the flight for free. I have ignored it for now but I am wondering how long I can wait to respond. Will they take action if I continue to ignore them? I'd love to be able to wait until I make a decision and cancel then for free.