Using the 7 draw

Are there some rules of thumb about when and when not to play the 7 draw? I hear players - Gary Smith, for example - glissing up to it briefly or using it as a passing note (or is it passing tone?) on a run down the harp. I know as well that you used the 3 draw unbent - very briefly - as a cool dissonant note in My Blues. Would you treat the 7 draw in the same way ie. sparingly and either as a passing note or deliberately dissonant note?