I’ve worked at companies that did Myers-Briggs/Keirsey temperament testing on people, and just for fun decided to try out another couple of tests over the last couple of months, most recently at mypersonality.info. It seems my personality type wanders, from INTJ to INTP and over to ISTJ. Either that, or I look at myself differently on different days, or respond unexpectedly to nuances in questions. At least two of the four axes are reasonably stable, even if the other two aren’t. Fortunately nobody I know takes this stuff too seriously; as the sites say, these are all tendencies rather than absolutes.
Another interesting point: all three of those personality types are said to be more prevalent in males than females. And probably more prevalent in the career path I’ve chosen as well.