Open strings should be used as and when needed and never overlooked when playing a riff that requires a large shift of position, if an open string can be used to make a change of position smoother.
I have included a PDF file which demonstrates this. It so happens that the two examples are very similar but these are the only two transcriptions I could think of where the open string could be used in this way.. Both are Stevie Wonder songs so it could be that is why they are similar. I am also aware my explanation of playing in position deserves a better explanation if I have not made myself 100% clear.
One final note, why not play an open string with the same note fretted or even alternating between the two, mute one and play the other etc.etc.
[attachment=101305:Position.pdf]