When I start to feel the need to get a stop watch out in order to see how fast I can get a return done, then it's time for me to retire.  My intent is to take as much time as I need to make sure that the return is done right and the client is reasonably happy (sometimes those large balance dues happen).  Preparing amended returns is something I rarely do (other than to fix what another preparer screwed up) and I would kinda like to keep it that way.