i actually did just that. flew ewr- hkg in H....about a week before my return date, i called up the reservations desk (oh, and i had already been upgraded to bf) to have them switch my date to two weeks later. i already went to the website to make sure that the same flight would be ht esame price- no problems- they charged me the 250 change fee plus 25bucks for a saturday flight. that was it.

and luckily i was able to also move my bf upgrade to the new date too...