A few days generally

We don't always make a good first impressions, so you can't always tell if the other person is compatible within meeting them. It's always nice when that happens though, I once had a pretty satisfying conversation with the person sitting next to me on a plane.

Everything I do. I do it for you

It's pretty much immediate that I know when I'm going to vibe with someone, I make some ridiculous comment and they are interested or laugh and they don't back away slowly, I know I'm good 👍

IRL it's probably a few seconds (minimum, at least). Online it's gotta be like 6 to a dozen posts I guess, idk. I guess it's mostly communication IRL and in videos? If you include body language, intonation, etc. in communication? It's also possibly appearance, clothes, voice, aura, etc. And online in text it's almost entirely communication. When I say "communication" I don't necessarily mean between me and them--usually it's a one-way thing, I just see their public content..

Its an initial feeling (chemistry) and then time to experience their principles and morals.