Sorry, no experience with canceling/re-booking. But do keep in mind that EVA will open up a lot of seats as you get close in to your departure. Granted, a bit trickier with more than 1 pax, but depending on the flight I suspect you won't get stuck. If it's BR15 then I don't think that I've seen the premium cabins much more than half full recently. And yes, some very nice 'T' fares right now.