I can use every cognitive function with equal strength, my ability to tap into every avenue of the brain unparralled. It's a blessing and curse, and my initials are JC, so I've come to some pretty obvious conclusions.
:laughing: Please hold on a minute while I grovel in worship! [To the reader: count one minute in solemn reverence for @rpmcmurphy47
In response to the OP: I think the answer to your question really depends on the theory you subscribe to. I originally tested (consistently) as an INTJ, then (consistently) as an INTP, and eventually as an INFJ (again, consistently). There are several ways of explaining it:
One possibility is that my order of preference for the functions changed from Ni, Te, Fi, Se, to a more prominent Ti, to a tertiary Ti and more prominent Ni-Fe. If this is your way of reasoning it out then that means that I would have basically changed functions.
Another possibility is that I have a set of strong functions (say Ni, Ti, Fe, Fi, or something...) that have changed order and affected my test results. This could explain the different results to an extent, and wouldn't require any momentous/pivotal change in the ordering of all my functions.
It also could be that the tests focused more heavily on dichotomies and that my F/T and J/P dichotomies are not pronounced, so changes in my environment were enough to nudge me into a different type.
I personally am not sure that it makes sense to talk about all 8 functions in a single individual. The reason I say that is because the functions are not fully dissociated and tend to overlap quite a bit. This means that Fi-like thoughts and behavior can be achieved by an Fe-dom simply by combining Fe with an introverted perception function. I'm not convinced that each of the 8 functions corresponds to an identifiable pattern of brain activity or anything of the sort, and short of that there's no way of telling whether one person's Fi corresponds to another's in any concrete way.
That was a long-winded way of saying that I don't buy any of the 3 explanations that I've outlined above.
I think that functions build on themselves from an early age. If you, for whatever reason, start using Te as a toddler, then that part of your brain will develop, people will praise Te behavior in you, and you will be able to meet an increasing number of your daily needs with Te, so why bother with Fe? or Ti?
As you mature though, you'll gain self-awareness, and that will lead you to try to compensate for the short-comings of Te by looking first to Si or Ni, (not Ne/Se and Fi since the tert and inf functions emerge as shadows alongside the dom and aux), and then eventually you will seek to emulate the benefits of Fe, Ti, etc that you see in others. Over this period of self-criticism/self-discovery you're likely to identify more with the functions that you're paying the most attention to. BUT
Te is so deeply rooted in your thought process that it's still at the core of your personality, even though you might not see it.
TL;DR I think most people are stuck with a system of only 4 functions by the time they're teenagers. I'm not saying it's impossible for functions to change, but I do believe that there's a self-reinforcing mechanism that makes it very unlikely. Changes in type are more likely a result of self-discovery and/or mistyping.