tbf, there are some people I interact with daily that I barely know just because there aren't that many appropriate opportunities to open up, be vulnerable, and talk about your deepest, darkest sheeit. But if there were a moderate number of opportunities on a regular basis to do that, probably a few months (ballparking it). I like to open up to people so we can get to know each other, but in some circumstances it's harder to make that happen just because of the setting we're in (grad school in this case)