Many of you are likely more knowledgeable than I about this,but I made the transition to 50 to 60 a few years ago and have never looked back.I have had injuries and physical therapy to both shoulders andit no longer made sense tobe at 60 to 70.
Anarchery instructor once told me that if the expression on your face changes when you draw your bow you are drawing to much weight,he also suggested sitting on the ground and attempting to draw your bow to see if you are over bowed.
I understand matching your physical ability to your hunting conditions and everybody should do whats right for themselves.There are a lot of accomplished hunters who kill all kinds of big game at draw weights in the 50's. I had a completepass through on a black bear a couple of years ago at 56 pounds.The bear was 225 pounds,not a monster but a better than average bear for the catskill mountains here in NYS.I was also using mechanical heads.
I don't think KE is an issue.