I think the typical thinking is that it is unchanging for the most part, but extreme circumstances can greatly affect one's personality. I think it is perhaps a reliable point in time assessment. Teams I have worked with seem to find value in better understanding themselves and their current patterns as well as those of their teammates. It generally leads to better collaboration even if things shift over time. Any assessment system is dubious when it seeks to label subjects that are perpetually changing.

Personally, I feel there is value in understanding each of the aspects as a spectrum so one can underatand their behavior in comparison to the opposite at any given moment. So if you understand the qualities of an introvert and an extrovert you can work to balance yourself and draw from one side another depending on which might serve you more in a given situation. So one might be an introvert, but needs a change. They can foster their extroverted qualities to experience a more social state. The same can be said for Sensing/intuitive, thinking/feeling, and judging/perceptive.

Just my opinion.