having an autopilot is like going to the gym for 1000 hours a year...and only getting on the treadmill for 2 hours.
you have the body of someone going to the gym for 2 hours
so too with hand flying...if you hand flew 1000 hours, you would be tired, but darn sharp.
so, compromise...hand fly more, esp during climb and descent and use autopilot less...you will come out pretty sharp and a little tired