^The danger is my situation.
I started when I was 27, thinking I wanted nothing else and would in any case get through quickly because I was "super smart." As it turns out, 1) getting a Ph.D. requires much more than smarts; 2) idiosyncrasies exist that slow you down no matter how smart you are, how hard you work, or how much you produce(e.g. committee bullsh*t); and 3) your lumps can wear you down and crush your expectations and you may end up not wanting to do this for a living. And then what? You're in your 30s and light years behind other people your age in terms of experience. Not a great situation to be in.