I have to actively work on keeping a regular day night cycle. I am managing right now, but only because of prescription drugs where one of the side-effects is drowsiness.
I'm a vampire too, my creativity and drive peaks at around 1am if I leave my body to its own devices. And I can get by on 4 hours of sleep per day, but apparently that is not good for you in the long run, so I induce 6 to 7 hours where possible.