I think you will answer your own question if you are still shooting the bow when you reach a certain age. Beyond that age, which varies with individuals, every year you are capable of doing a little less than you could the year before. Generally, parts of the body, shoulders, knees, feet, hips, etc., that may have been overused or injured earlier in life begin to wear out and fail. Life becomes more of an orderly retreat, or at least we try to make it orderly, than a victorious advance.
I don't mean to make this sound negative, because I don't feel that way, and neither do the other people of my age who continue shooting, albeit lighter bows than we used to shoot. Instead, we find our victories in continuing to do the things the good Lord allows us to continue doing for as long as we are able to do them.
Do what you can while you're young, but be wise about it. If I hadn't run so many marathons in my 40's, maybe I could still be running today. If some people in their 70's hadn't pulled so many 70# bows when they were younger, maybe they could still be pulling 40# bows today.