( okay, celebrities) wear short dress lengths because they can. They are flaunting their well preserved bodies as a visual rebuke to middle age. I think more than the question of length alone is the idea of presenting a sophisticated front versus the kind of forever girlish thing one sees on The Real Housewives of -wherever.  For my eye, a mid-thigh length in a dress or skirt that is also girlish or retro reads 'young' rather than  'youthful' and style aware. A middle-aged woman has a little more leeway in something short but clean -lined and grown-up. That said, I think mid-thigh is a bit too short. Why? Because subtlety is sexier than anything obvious. Just ask any french woman. Show off your great legs with a hemline at just above or even a few inches above your knee. Create a focal point with you gams instead of an exclamation point.