Can a bad, consistent cough damage my neck lift?

Its highly unlikely after 9 weeks that you have caused any damage, most of the initial healing is done so don't worry about damaging your results. 

Dear. Troylin,Thanks for your question. At 9 weeks post op, I think you'll be fine. However, I would definitely suggest that you see your doctor to address the cough. Hope you feel better soon.Kindly,Kouros Azar

So the soft tissues of the face heal pretty quickly. 9 weeks should be enough to have everything stuck down now unless you have a very heavy cough. I have heard of post op complications as late as three weeks to do with coughing but that the longest time.Hope that helps. Adam Goodwin