A simple look at old photos shows that people change and don't do so overnight.

Gonna go with a "yes" here, if for no other reason than to rightfully piss all over the "type is fixed and inborn" hype.

Take a sine wave:



Have this thing as a 2d physical landscape of sorts. Drop a 2d marble in there. It'll sway and waver a bit before setting into a well. It won't get out of there if conditions remain the same. It would take one hell of a push to roll that stone from out of any well, representative of any functional axis, up the side, over the hill, and it into an adjacent well, representative of that functional axis's counterpart (Fe/Ti to Te/Fi, Se/Ni to Ne/Si).

Hell, this thing, given a 3rd dimension, can take on all the quadras! Check it:



This leaves other questions open, like if the depths of these wells deepen or shallow their landscape over time, with types becoming more or less entrenched and absolute, given... stuff... (yes, I gotta look at a concept like this before I really start to get it haha)...

I've got Dave Grohl as having moved from Ne-IEE to Fi-IEE over the course of around a decade. Something that gradual is by nature difficult to pin down; thankfully, the dude left a huge trail... I'll be on the lookout for balls-out type changes, with my eyes set squarely on Mike Patton...