Well since this ancient thread got bumped I've twice been asked if it was possible to change my vacation time in the 20 years I've been at my job. One time I flat out said no since the friend I was going to visit called in a few favors to take the entire time I was there off. The other time I said sure as long as they were going to cover the change fee(s) and any difference in cost for my tickets. Needless to say I took both trips when scheduled. Their reason for asking? Lack of coverage. Sorry but when I put in a request, that's approved, for vacation time in July back in February it's not my problem if you can't find coverage especially when I reminded them several times as the date grew closer.