There is no universal answer to this. But here is a framework that holds up better than most.
**Three visits. Each one does something different.**
The first visit is to fall in love. Everything is heightened. The novelty is real and you should let it be real. Do not try to be clinical about it. You are there to find out if there is something worth pursuing - and if there is, you will feel it. This visit is supposed to sweep you a little.
The second visit is to fall out of love - or at least to stress-test what you felt. This is the visit where true colours come up. Where the things she glossed over on calls become present. Where his habits and moods and family dynamics become real rather than described. If you make it through the second visit still sure, that means something.
The third visit is to be certain. By this point you have seen the best, you have seen the friction, and you are deciding whether this is the person you want to choose every day. This is the visit where serious discernment about a timeline begins.
That said - how many visits you need also depends on what is available to you. If you have family or community around you who know you well and can weigh in, you can move with more confidence at each stage. If you are entirely on your own in this discernment, take more time. The people who know you best are a check on your blind spots.
There is no shame in needing a fourth visit. There is also no virtue in dragging it out indefinitely once you know. At some point the distance stops being a phase of discernment and starts being a reason to avoid commitment. Know which one you are in.