Anyone know for sure if you cast an all day spell and then rest after a battle if you need to recast the spell or not? I have been recasting but would like to save spell points if I can. Like the Protection Magic spell for example.

I would always cast again because that's how MM1 worked, but I don't know for sure. I think there is a way to check which spells are active, but I forget what it is. If you check the manual to find out how to check active spells, then you could test it by casting the spell, then resting, then checking to see if it is still active.

Anyone else know for sure?

No, you have to recast. I actually looked at the screen this time (duh) and noticed where it shows how much light , magic, etc you are using.

I thought that might be the case. I think that spells will last one day, but always expire when you rest, even if you rest for less than one day.

So if you go a whole day without resting, the spells expire and you have to cast them again. Otherwise, they reset when resting.

In MM3 and WoX the spells expire when you rest and at sunrise, it might be the same in MM2.