My longest solo lock ever was roughly a week, however one of the few times my partner(they/them) took part in the play, they kept me locked somewhere between one and a half weeks to 2 and a half weeks. They told me not to keep track of the days after a weeks time. The reason being because various things kept happening. Our friend came over spontaneously, we had to go on a road trip, my partner kept getting called in to work... it ended up being a very long but extremely sexy period of time.