How many nights do you need on the Athens Riviera?

One to three nights, and which end of the trip you spend them on matters more than how many.

The arrival case is about arithmetic. A morning flight from the States lands you at Athens mid-to-late morning, and hotel check-in along this coast is commonly mid-afternoon — so there is a gap of several hours between clearing passport control and having a room. That gap is not a problem unless you have planned as though it does not exist.

Leave the bags at the desk, get in the water or sit down to a long lunch, and the first day becomes part of the trip instead of a write-off. One night here does that job well.

Budget more time than you think for the first passage through passport control, too, since the biometric enrollment on a first entry happens in the queue. It compresses the morning that is already the most tired one.

The departure case is the stronger argument, and it is the one most itineraries get wrong. Two or three nights at the end turns the last stretch of the trip into a stay rather than a logistics exercise, and where you base yourself matters more than the count. The alternative — a final night in the city, an early alarm and a drive across town with luggage — spends your last day on transport. Here you are half an hour from the terminal, which means a beach morning is still possible on the day before you fly, and the drive itself is short and early enough to be uneventful.

Beyond three nights the Riviera can certainly hold you: there are enough beaches, the coast road runs to Cape Sounion, and the city is a day trip rather than an expedition. But on most itineraries this is the bookends rather than the middle, and the honest reason to add nights here is that you want a rest at the end, not that you are running out of things to see.