My take on this is that in order for these rules to be valid they would have had to do some studies on flight crews and how fatigue affected them. If the studies are 60 years old then they obviously didn't have the same environment that we experience now. Somehow I think these limitations were set knowing that they would never even get close to those kinds of duty limits. I could be wrong but I don't think the average pilot had 5-6 leg days 60 years ago. Another thing I could be wrong about is the kind of weather they would fly in. I would think that 60 years ago there were probably many times when a flight couldn't dispatch due to low visibility. Now a days we fly things to some pretty low minimums and a few times a day might I add. Does anyone have a similar take on this?