I think it depends on the person. I'm 44, growing in my gray (I am very salt & pepper at this point), and I have very curly hair that's past my shoulders. That's "long" for me. I think clothing and what a person does with skincare and makeup contributes to the "aging" look as much or more than hair length. Also, no sense having longer hair if it will not be maintained to look healthy.
I think it depends on the individual. If you have an oval face and prominant features like cheekbones and eyes, it can look great. Otherwise you just look mannish as it can be very severe.
I think it depends on the cut!
I had short cuts years ago I know I looked great , but I think you need it softer, mine is too long my family tell me I should go to shoulder length I know they are right ,cant bring myself to cut it, I do get it trimmed etc every few weeks..everyone one over 50 here wears their hair short they look a bit butch ..but they stay cool and I guess butch is okay.