Do spells with a duration >8 hours last after resting?

Question

In our last session the PC's prepared an attack on drow. One PC had caster level 13 and intended to cast darkvision before resting with a duration of 13 hours. So after 9 hours resting and preparing spells for the next day there would still be 4 hours of darkvision left.

Is that legal? It does not conflict with the recent casting limit because the spell is cast more than 8 hours before preparing new spells. So, technically it is ok, I suppose, but it feels like an "extra spell" and it opens the door for preparing a fight with spells cast the other day.

Answer 1

Yes

Its perfectly viable. There is nothing in the rules saying that spells only last until you rest. And there are spells with durations that will last much longer than that (Contingency for example lasts 1 day per caster level and has a much stronger effect).

The darkvision will only last 4 hours into the day, and he will either need to recast it later (if the fight doesn't happen in that period or it runs out DURING the fight) or just deal with it not being there the whole day. If your players have spells left over at the end of the day and they want to use them to benefit them later (say casting healing spells before resting) it is completely up to them. If something happens upon them in the night and he wanted to use that spell slot then, he wouldn't have it.