I just asked my "resident 12-year-old"- how old is mid-life? She looked at me (like a 12-year-old) and said, "I don't know, 30" . WHAT!?!  That cannot be, what does a tween know about MIDDLE AGE! I think 30 is still in your "quarter life crisis" phase! I mean, at 30 I still had a metabolism and stayed up past the double digits! So, I naturally went to my second favorite source- the internet. Thank you, Cleveland Clinic, for validating me. Just as I thought, midlife is 40-60 y