A therapist each, and what it buys on a short evening
A therapist each means two women in the room and two sessions running side by side, which fits the same evening into roughly half the elapsed time.
Two arrangements put both of you in the same evening. One therapist between you works with one partner at a time while the other stays close, and the hour has a conversational rhythm. A therapist each means the two sessions run in parallel, and the whole evening finishes in about half the clock time.
How the two compare on the bill
Sharing one therapist is the lower hourly rate, and a therapist each is exactly twice it at every length from the first hour to the third. Ninety minutes with a therapist each therefore costs the same as three hours with one therapist between you, which is a useful way to weigh time against money on a short night. Every one of these is printed in the profiles on the roster, which is the only place on this site where the figures live.
Why a working week tends to choose it
Because the constraint on a weekday is rarely money and almost always the clock. A couple with a nine o'clock start the next morning can either cut ninety minutes to an hour or keep ninety minutes and halve the elapsed time. The second answer leaves more of the evening intact, which is the argument made at length in the three day plan.
The room has to take it
Two sessions side by side need floor space beside the bed, somewhere for a second set of things, and a bathroom that two people can use in sequence without a queue. A standard double room usually manages. A small room with the bed against a wall usually does not, and it is worth saying so in the thread.
Always half ahead
Any booking with two therapists carries an advance half whatever its length and however far off it is, which the deposit entry explains.