The duration ladder is the fixed price list every booking is drawn from: session length and the number of therapists set the figure, and nothing about the flight changes it.
Airfares move with the date, the cabin and the hour you search. The ladder does not move at all. It is a short list of session lengths, each with one price, applied identically to a room on the terminal's doorstep and one on the canal ring, whether the session starts after lunch or before dawn.
A two-therapist overnight is not on the list and is not quoted.
Travellers rarely choose a length for its own sake. They choose it from the gap they have. A long connection with a day room leaves space for ninety minutes and a shower without watching the clock. A landing at 22:00 with a meeting at nine allows a firm two hours and a proper sleep afterwards. A missed connection that has turned into a whole night at an airport hotel is where the overnight enters the conversation. Leave margin at both ends: the rung counts the time with her, not the minutes you need to dress, repack and reach the gate. The layover entry shows how to measure that margin.
Length also decides part of how a booking is paid. Three hours or more always confirms with half in advance: a single therapist's EUR 540 becomes EUR 270 up front, and a pair's EUR 1,080 becomes EUR 540 up front. Shorter rungs carry the deposit too whenever another condition applies, among them any booking at Schiphol or an airport hotel and any first booking. The price page keeps the ladder current, and the deposit entry lists every condition.
One hour EUR 180 through to eight hours at EUR 1,250. Forty to sixty minutes anywhere in the centre; the Schiphol airport hotels by arrangement.