Your goal should be to get to the destination as fast as possible.
"Lean" tells you that small batches reduce the waste.
As an analogy, think about looking in front at the road that unwinds passing through cities and attractions until finally it becomes too small to see ahead. You feel that if you stay on the road, it will likely bring you to your destination.
Nevertheless you are not sure. As you move ahead it gets clearer were you are and where you will have to go.
So how far should you go before stopping?
It depends. It is all about how far you can see and how confident you are that it is the right road.
If you do not see too far ahead, it is probably a good idea to just reach the next city at hand and spend some time checking if you are on the right road. Otherwise you may waste time going too far on the wrong path. The further you go, the further you will have to backtrack.
But if you can see further ahead, you want to move faster and skip the pitstop.
This analogy only goes so far. But depending what you are building and were you are in process, and more importantly, how sure you are of what you actually need to build, you may less time in planning and just building what is merely necessary vs building a more complex architecture.
So you may say: "let's try to find as much we have to go and where before we start. But even the pathfinding activity takes time...