Update and observation.    I changed the ip address to  something other than the default.  The camera stayed connected over 24 hrs using the smartPSS program.  However the second I tried to access the webserver through a browser the camera rebooted.    It did come back online eventually.  Sure would like to fix this issue.  I have plans to put this camera in a very remote inaccessible location.   Need maximum reliability .      So far I do not have that confidence.
update - forget the above, this time when it went down, smartPSS  did not work either.  Port Scanner shows port 554 open, but no HTTP service.   I can ping the camera's IP so  I know it is still connected to my network.    Reboot (unplug - plug) everything comes back online.    From what I can tell, I'm not alone with this problem.    Hoping collectively someone  or Dahua will have a fix.
More observations over the weekend.    Reflashed with the most current firmware off of the Dahua site.  No change.    
I did check the external power supply and found out it was not providing power.  I always had the camera plugged into a poe port so perhaps I never did have external power during testing.  However, other working  power supplys do not work now when plugged into the camera.  I can only get the camera to boot  through the poe.   I did notice that the power supply the came in the box was  labeled 24volt  3A.  Unclear if this camera can handle 24 volt.  I wouldn't know if the power supply  initially was working and then fried something from the over voltage.  All I know now is the  power brick provides 0 volts (when checked with a voltmeter) and the camera's external voltage connection does not appear to work (when tested with a working 12 volt 1.5A power supply).   I believe this issue is unrelated to  the losing web connection after a few hours after boot.  
I connected the camera to  my 
BlueIris machine.  The camera has been running  (video showing in BI) for over 36 hours now (never lost connection).    However, I cannot access the internal  webserver.  Nor can I control the ptz with BI.  Initially after boot, BI can control the PTZ.  So the loss of  webserver access and ptz control within BI seem to be related  to the same issue(s).
Port scanner  shows an active connection with ports 554, 1935,  5000 and 37777 T(TCP) open.
Someone on this forum had similar issues and downgraded firmware fixed it.  Would like to try that but I do not know where to find older firmware.