takasi said:It's incredibly useful for utility spell selection.
For example, in our last session we were exploring the underdark when the party approached a lake we needed to cross. We "befriended" a koa-toa, but there was no way that my craven cleric was going to get in a fish-man's boat without some insurance. We asked him to wait a few minutes so I could cast water walk.
Later on this had a huge payoff. A group of koa-toas attacked us on a large staircase on the other side of the lake, and one of them bull-rushed the party wizard over the ledge into the lake. The koa-toa fell into the water expecting the weak land-walker to fall in with him...
They're burned.gnfnrf said:But then, when does the recent casting time count from?
Say a cleric who prepares at dawn gets attacked at four in the morning, and casts a bunch of spells. Can he leave them empty at dawn, then fill them at noon (once the 8 hour limit is up?) Or are they burned for the whole day if they aren't ready to cycle at dawn?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.