I did this on my first flight with the Inspire just to get the hang of the aircraft before attaching a camera. Ever since then, I never fly without the camera or without filming. For me, the two go hand in hand. I'm always practicing flying and shooting in tandem.
My guess is you'll get a few 3 minutes or so extra flight time without the X5 attached. Pretty sure the X5 vs X3 flight time difference is around 3 minutes while only hovering.