Overnight, the eight hour block for two
A fixed block of eight hours with both ends written into the confirmation, at 2,500 euros for two guests with one therapist.
Overnight is a format with a fixed length rather than a mood. Eight hours, with the start and the finish both written into the confirmation so that nobody is working anything out at five in the morning.
The four figures
Two guests with one therapist: 2,500 euros. Two guests with a therapist each: 5,760. One guest with one therapist: 1,250. One guest with two therapists: 2,880. Half of whichever applies goes ahead whatever the notice, because every eight hour block carries a deposit.
What it is not
It is not eight hours of massage, and booking it on that expectation is the one way to be disappointed by it. It is a long unhurried night in which an arrangement is part of what happens rather than the whole of it, with sleep somewhere inside it.
Where it fits on a reunion trip
On a night with a free morning behind it, which on a three night visit means the middle night rather than the last. Two departures on a Sunday morning and an eight hour block ending at six are not compatible, whatever either of you feels about it at midnight. Where both flights are genuinely late in the day, the last night becomes reasonable again. The overnight page goes through the hours in detail.