I don't think there is anything unethical about it. If you have the miles than you should be allowed, especially if it concerns different travel dates. As much as we'd all like to be able to set plans in stone all at one time, it often doesn't happen. Award seat availability is so variable that one often has to make a reservation when they see their desired number of seats pop up for chosen dates. Outbound and/or return dates often are not set yet so better to get them while you see availability then to wait and find out everything is gone. If you don't use them, the seats go back into the award pool for someone else. All of us know on FT, that we have to check on a daily basis for award availability anyways.