I have great success and turn only twice or three times a day. A mother bird sure doesn't count or turn every egg like clockwork.Studies indicate that the more frequently that eggs are turned especially during the early days of incubation, the better it is for the hatchlings. At least one poster has posted that she never turns her eggs. Personally I am lazy so I use an auto turner which turns my eggs every 3 hours.
Hatching Eggs 101 by @Sally Sunshine is an excellent source of information.