Long time friend has installed and serviced heat/air for number of years. Recent
problem under warranty was not resolved after several visits, changing parts,
etc. Stopped responding to numerous emails asking when coming back, how to fix
problem, etc. Reached end of rope and hired another company who fixed problem in
one short visit. The fix was something I had suggested to friend to try on next
visit

Friend will no longer receive my business nor referenced to others.  

To answer your question. Sometimes you reach the end of being reasonable!