Preparing spells at intervals through the day

[Ingenwulf]

A cleric has an initial time of day when they prepare spells, and they can't prepare spell slots that they have used in the previous 8 hours. Fair enough. However, page 220 of the core rulebook states that slots can be left empty and some spells prepared later in the day. As clerics do not need rest pre spell learning can they not then use up slots later in the day that have now been empty for over 8 hours? At the moment a cleric has it tricky if they do not pray at dawn or early in the day before heading off to adventure. A cleric learning spells at dusk will probably not be able to learn any spells atall if he has just been off for a hard adventuring day. is it preferable that the cleric prays at dusk to affirm himself for the day ahead but then tops up his 'empty' slots in the morning after they have been unused for 8 hours?, or do we all need to pray at dawn or adventure at night to gain a useable cleric. Please note i'm mostly trying to get flavour here, not find an excuse to get more than my alloted spells for the day. How does it work out for eberyone else?

[reefwood]

Here is an analogy that I just came up with... imagine that your spell slots are chalkboards. The time of day that you pray is the one time of day that you can wipe them totally clean and make way for the "writing" of fresh spells for the day. When you cast a spell, you smudge the "writing" off, but there are still chalk stains all over the board, so you cannot "write" anything else until you are able to completely wipe clean the boards...which is what happens when you pray. And for whatever reason, if you smudge the writing within 8 hours of praying, it cannot be wiped off. I guess if the chalk is smudged, 8 hours have to pass before it can be completely wiped off. But chalk that isn't smudged (i.e. spells not cast) can be wiped off without a problem.

As for leaving spell slots open... you pray for the day to wipe off the chalkboard, but instead of "writing" fresh spells onto each chalkboard, you leave a few blank, and you "write" fresh spells onto those later by taking additional time to pray. But if you weren't able to wipe off certain boards during regular prayer time (because those spells were cast less than 8 hours before praying), then those chalkboards are still smudged, so you cannot write fresh spells on them, and your wiping (i.e. prayer) time has already passed, so you have to wait for the next prayer time to wipe off these remaining smudged chalkboards.

Anyway, I understand the rules to say that any spell slots that cannot be filled during your main preparation for the day cannot be prepared later in the day either. You have to wait til tomorrow.