No, people do not change. People who say that their personality fluctuates from this to that to this didn't know themselves to begin with. People grow, mature, and amass experience, but the core of what makes them themselves does not change. There is a popular trait construct in psychology called "The Big Five", and it has a list of traits, some of which don't seem inherently "good" in our culture. There has been a significant amount of research into this trait construct and it has actually been found that people, in fact, do not change. It was amussing listening to my classmates battling my professor on this when presented with this information. People do not change, and it is something I have come to see vividly for myself. Every long-term relationship I have ever had has been a clear example of this, despite how much they learn and grow. It is the same with MBTI...
The valid argument that appears to be change is to say that we may become skilled at using functions that are not our dominant functions, but it does not change what our dominant functions are.
