Spell durations - who knows?

[Quasqueton]

Do/should spellcasters know how long their variable-length spells will last? How about the targets of the variable-length spells?

How do you determine whether a set-length spell's duration is still on near the estimated end of its time? For instance, say the mage has a spell in effect that lasts 30 minutes. The party reaches their destination where they will now fight the BBEG. The Player asks, "How long did it take us to get here?" The DM replies, "Oh, about half an hour." The Player: "Well, is my spell still up? I could use it for this battle."

How do you determine whether the spell is still in effect for the coming battle? 50/50 chance (coin flip)? Spellcraft check? DM fiat?

How about a set-length spell cast on someone else? Does/should the recipiant of a buff know it will last 4 minutes? Does/should the recipiant know when it is about to end? How about the target of a hostile spell?

Quasqueton

 

[Orm]

A caster should be able to estimate the duration of any given spell. After all you need lots of experience and training to cast spells. For medium/long duration spells that are about to end in the nearest future -like what you mentioned- it´s up to the DM to flip a coin or roll % or whatever. Besides, often it´s simple to observe the spell effect to determine wether the spell is effective or not (e.g. bull´s strength).

Orm

 

[Rel]

Nobody but me (the DM) knows how long an offensive, variable duration spell will last. I don't tell the player when they cast such a spell and I don't tell them when one is cast on them. I also have the NPC's act in such a way that they don't know when the spell will end. If the NPC is unfamiliar with magic I sometimes have them act as though the spell is permanent. It takes more work for me this way but I think it heightens the tension.

For longer duration spells I try not to think about what the players have cast (this is usually easy since I'm juggling a lot of balls as DM). I'll say, "After about two and a half hours, you reach your objective. Roll initiative." If they have spells that are definately still running or expired then there is no question and if they are iffy then I'll probably give them the benefit of the doubt and secretly roll dice to see how long the effect will continue to last. Again, if it has the possibility of running out in mid-combat then I think it makes things more exciting.

 

[Thornir Alekeg]

I allow the players to know the duration of spells they cast. I make the assumption that the caster knows how well his or her spell was cast, and has a connection to that spell, especially ones that can be dismissed (it also allows me to keep things moving by having the player make any rolls for duration while I am determining saves).

I do not allow players to know the duration of spells cast upon them by opponents, but, like the PCs, the opponents know how long their own spells will last and can stragegize accordingly.