I discovered MBTI back in 1996, when I was 27 or so.
I'm 40 now.
Finding it was an "aha!" moment for me, and really changed my attitude towards myself and others. Lots less guilt, lots less resentment. I finally knew (generally) who I was and that I wasn't 'weird' ... or alone.
INtP from the first despite looking and studying types and functions and whatever else. I just really like using my N publicly more than my T; and even when I think privately, I tend to focus more on exploration first and making sure all options were considered.