1.) All spell effects cast by Prepared Caster, if they choose to re-prepare spells, are ended. Including spells that last the whole day. This represents the wizard sucking all possible expended ambient energy back into them in order to re-prepare their spell list.
2.) Some areas restrict this ability. E.g., trying to re-prepare spells in Waukeem's Rest will result in a pop-up: "Preparing spells takes time, and you are currently in an area where time is important."
Hag lair: "Preparing spells requires time spent vulnerable, and you don't feel safe enough to do so." This could match up with areas where fast travel is prohibited and/or long resting once you reach that area would advance effects.
+1
