I'd like to add my own experience from TPE, in case someone finds it useful. As most of you know, CX has tons of flights TPE-HKG every day. I arrived early (around 5h) to enjoy the lounge. I had luggage to check-in. Despite the check-in desks being open all day and flights leaving all the time, I was not allowed to check-in earlier than 3h before departure. Funny story, the ticket desks did not mind at all changing my Y ticket for free to an earlier flight