Good work Mark. I think that "long exposure" it's only a conventional denomination. "Long", normally refers to these ranges of time exposure that we can "take in hands". But, if you are an extremely quiet and solid man, probably might shot at 1/3seg without tripod...then whats the longer exposure time? I think that "long exposure" is a relative concept about the velocity, not from the camera exposition lapse, but to the quickly movement of the subject, not only this also in relation with it's environment.
Thats why i think that 1/3seg it's an enough long exposure for this shot.