Because most endings branch from Day 7, keeping a save file at the start of that day allows you to quickly replay and select different dialogue options.
The game was officially noted as having "all endings finished" as early as 2013, with subsequent updates focusing on refining animations for each specific player action. Video Of Touch And Tease Vol 3 All Endings Kcttztit
Unlocking the full range of conclusions depends on a secret room located in the alchemy lab. Players must open this room by interacting with the box on the shelf (the one Theo explicitly warns you not to point at) and entering their name. Because most endings branch from Day 7, keeping