I'm getting 4-6 hours with high brightness doing more CPU/GPU intense things, and easily 7-10 hours or more with half or lower brightness and consciously working to get the most out of my battery.
Have you done a calibration? I had to do it twice within 5 days of getting my MBA 13", but after that I noticed a considerable improvement in my battery life.
Also, are you facetime chatting for three hours straight??? of COURSE that will drain the battery. If you do some research, you'll see that skype video chats and iChat video chats are also a big drain on the battery. this is to be expected, and if you plan on being in a video conference for hours on end, you should definitely be plugged into A/C.