I weigh in every morning, knowing and accepting that my weight will fluctuate by a pound or so up or down, every day. But my daily date with the scale keeps me aware of my commitment to maintaining my weight loss.
I don't get upset by fluctuations--if I did, I would drive myself crazy. But I have a range that I need to stay inside. If I go out of it, I have a few days of huge yummy salads to get me back to the safe zone.
I found in the past that if I stopped weighing myself daily, I would start to backslide. But that's just me.