I never understand who anyone expects someone else to answer the question of, 'how long should I spend in X?'

The answer to that question depends on your interests, what you want to see and do in a given location. One person may say, 'a day was enough for me' and another says, 'I visited for 2 weeks and still didn't get to see and do all I wanted to.' It is a 'how long is a piece of string' question. What's more, it assumes you know beforehand all that you will find of interest to see and do in a given place.

Most people planning some kind of multi-destination vacation tend to approach it from a specific perspective. 'I have 14 days and 4 places I want to visit, how do I divide my time up?' It isn't the only way to approach it however. What about, 'I have 14 days, how many of these 4 places of interest to me can I visit and see and do all I want to do in each of them? That might well get you a different answer. It also however, assumes you can know beforehand everything that will be of interest to you in each.

I take a third approach. I may have 4 places I would like to visit and 14 days to work with. I go to the first place and stay until I am ready to leave. That may be 1 day or all 14 days. I don't know beforehand and don't believe anyone else can know beforehand either. When I have seen and done all that I find there of interest to me I move on. No sooner and no later. If I only get to 1, 2 or 3 of the 4 places, that's fine. It just leaves somewhere for the next time.

The common phrase used by people who start out with the first approach of dividing the time by the number of places they would like to visit, is 'I want to do as much as possible'. But they confuse the word 'much' with the word 'many'. They are not synonymous. The way to do as 'much as possible' is to spend your time in places doing what interests you, not spending time in between places. Every time you move, you lose time that could have been spent in a place doing things. So as in many things, less is more. The less you move, the more time you spend seeing and doing things. Do not get confused by quantity being equal to quality.

In any given day, you can only get so much out of that day. A good day is one in which you feel you got maximum enjoyment, experience, etc. out of that day. Whether you spend that day in A or B is irrelevant, it is what you got out of the day that matters. Travel can be as simple or as complex as you choose to make it. I prefer simple. Go to A, move on when you are ready. Rinse and repeat until either your money or your time runs out. Go home.