Roy Newberry did a survey for me a few weeks ago. It was about 6 to 7 hours with no AC in some really oppressive heat. He took his time and was very thorough, all the way to the top of the mast.
He was well recommended when I asked around. He will show you how anything on the boat works that you are unfamiliar with, show you all of his concerns about the boat and discuss any of yours. He emailed me a report the evening of the survey and he followed up with a call to discuss some further thoughts.