Cities are fractal. You can always go a layer deeper and there’s just as much complexity.

Following this principle, I sometimes think it might make sense to just stay in San Francisco my whole life and explore the infinite levels of that fractal. It’s cheaper than interstate or international travel anyway, and according to this framework you get the same amount of interestingness no matter how many levels deep you go.

The catch is that when you stay in one place it's too easy to accidentally fall into a rut and not actual get the most out of the levels available to you. So while it may be theoretically possible to see a wide variety of things and learn things at different levels by staying within the limits of a single city, you’re much less likely to surface those experiences because it’s easy to build up habits, a pattern of behavior that cut off interesting discoveries. This is an obstacle rather than a theoretical limit.

The other possible takeaway from viewing cities as fractals is that it doesn't matter how much time you spend in one. There'll always been an infinite amount of people, places, subcultures, foods, and more that you didn't get to experience. In other words, the one-day-per-city approach was fine for my recent trip to Asia. The limit on it is less how much you can see in a day (per its scale-free nature) and more how exhausting it can be to go from place to place. The main bottleneck here is the logistics, cost, and physical exhaustion. I wasn't responsible for planning the trip, which minimized these problems; if I had to organize the logistics of getting to/from the airport, lining up the schedule, etc, I would have wanted more breathing room in the schedule.

Of course I’d like to have spent more time in each city, but there would still be an infinite number of things I’ve missed. If you can reduce the overhead constant costs (which is a big "if"), there's no such a thing as spending too little (or too much!) time in a single city. There's always another layer deeper you can go.