I definitely agree that 3-9 months (especially at the low end of that range) isn't enough to feel sufficiently rooted somewhere, but one quick thing I would add is that I did all of this while speaking German fluently already, so my time in Germany at least was not consumed by trying to surmount any language barrier. I'm just someone who makes friends through my existing friends (instead of strangers), so starting from zero isn't something I do well.