I think we did a test in college when I was in my early twenties, but I didn't pay much attention to it. Was re-introduced to it by my dad when I was around thirty (he was exposed to it through an on-line match-making service). I am now thirty-nine.
“There are two novels that can change a bookish fourteen-year old’s life: The Lord of the Rings and Atlas Shrugged. One is a childish fantasy that often engenders a lifelong obsession with its unbelievable heroes, leading to an emotionally stunted, socially crippled adulthood, unable to deal with the real world. The other, of course, involves orcs.” ~ John Rogers
I first heard about MBTI when I was 13 tested as an ENFP and thought it was cool but left it at that because I had another obsession at the time, when I was 15 I got into MBTI some more and began testing as ENTPs and just generally identifying with NTs more than NFs. Now I'm almost 16 and I don't think I'll get bored of it any time soon, I got my best friends into MBTI so it's all good (ENFP and ISTJ)
Men are like parking spaces/the good ones are always taken and the ones left are handicapped or to small.
I don't recall exactly how old I was when I first came across it. Maybe fifteen. I kept getting INTJ or INFJ on online tests, which didn't seem to describe me well. I abandoned the theory for awhile, just started getting into it again this past year.