GuardTrails
What it means
An itinerary that strings three medieval towns together in one day does not give you three experiences. It gives you one, then diminishing returns. By the third stop you stay in the car.
But repetition is not guilty in itself. The word that matters is "unrequested". If sand, pines and fishing villages are precisely why you came, two sand spits are not saturation: they are what you came for.
How it is measured
By how close in meaning the stops of a single day are, judged on each stage's own description — not on a list of labels. Two stops that can be described with the same sentences compete with each other.
This count is the second of Is your itinerary too packed? Four counts to find out.
Two cases need telling apart. Stops that are too alike: that is saturation, and returns diminish. Stops with nothing in common, separated by a long drive: that is a collision, and neither belongs on that day.
Repeating a register that was explicitly requested is never devalued. The test fits in one question: did you ask for this register, or did the itinerary put it there?
An example
On our Baltic tour documents, the weakest day chained Viljandi, Valmiera and Cēsis (our trips). The three descriptive paragraphs share a skeleton, almost sentence for sentence: founded in the thirteenth century, castle of the Order, Hanseatic prosperity, Reformation, decline, independence in 1991.
When the description is interchangeable, so is the stop.
The same effect applies to a capital's major sites: three in one city act like three medieval towns in one day, which is why we limit ourselves to one major site per capital (see Two hours with a guide, then we walk).
What it does not say
The judgement depends on how finely the descriptions are written. Three baroque churches look alike to a generalist and not at all to an enthusiast — closeness is read at the resolution of the text, not of the traveller.