I remember reading some research that suggested that for every year you were "away" from a place that had been home, it would take about a month to adjust when/if you moved back. This accumulated additively up to about 9 years, at which point, "home" would never feel the same again.

So in that sense, it can be a "permanent" change.

I've also found those numbers roughly accurate, even for sub-year extended travel. I spent 6 months teaching in Berlin, and it definitely took a couple of weeks after returning to feel normal again.

That is, until you realize it is becoming permanent…