Mistwell
Crusty Old Meatwad
Actually, I think the more pertinent question vis-a-vis what you quoted me on, is can you "prepare" less than your allowed. If I can prepare 6, can I prepare 5 actual spells and 1 unprepared spell.
If, as I said, spells remain prepared from the prior day if you do not change them, then by definition you always your spells prepared. The rule is about when you can change your prepared spells.
The discussion of "when" goes to the point that well, I "prepared" my spells today, and if I prepared a "null" spell I can't prepare again until after a long rest.
How do you prepare a null spell? If you had something prepared the prior day, it's still prepared. I don't know of any rule that let's you un-prepare a spell and replace it with nothing - you can only change it to a different spell.