If you have only one headlight, then steady mode is certainly more appropriate for night riding. If your have one bike mounted light and a helmet mounted light, then I'd still keep both on steady in poorly-lit areas.

One case when a blinking headlight is appropriate at night is when you have two or more bike-mounted headlights. If the area is relatively well lit, then it might make sense to switch the helmet mounted light into blinking mode. (Of course, only where it is legal)