This came up in a fight against ghouls the other night, and while I ruled in the player's favor, it sparked a number of interesting questions that I couldn't find an answer to as written, so here's the example:
A ghoul moves up to a PC, strikes him, and the PC fails its fortitude save against its attack, enabling the ghoul's paralysis. As the 1d4+1 rounds is rolled, does:
A) the PC know how long to the exact round that he is paralyzed,
B) does the ghoul know the duration of its paralysis effect and,
C) does anyone else present (other ghouls or PCs) know this as well?
Obviously, this knowledge would likely affect the course of actions for both PC and the ghoul. For example, if the ghoul knew it only had 1 round before a highly dangerous combatant returned, it might be more inclined to coup-de-grace that individual than to attempt to paralyze others, where in a PC's case, he might neglect casting Remove Paralysis on his ally if he knew that he was about to un-paralyze. Also, does intelligence or any mental acuity play into the ability to deduce this? (would an iron golem 'know' that its breath is about to come back?).
Another example: A red dragon breathes on a group of PCs. Its recharge for the breath weapon is rolled, and it comes up 1 on the d4. Does either the red dragon or the PCs know the amount of time between breaths? Again, this knowledge would readily change tactics of both the PCs and the dragon.
Thoughts? I can't seem to find anything written supporting either.
My general assumption is that there are very few metagame elements of any RPG that could be known to the PCs or NPCs. So any random duration - I assume it is unknown and treat it accordingly.
I think this is one of those things that's entirely up to the GM. Maybe you rule that the dragon can "feel" how quickly the magic that powers its breath weapon is returning, or that the PCs have ways of estimating it. You could even allow them to make a Knowledge check to figure it out.
Same with the ghoul. Maybe the victim can recognize feeling returning to their limbs, or the ghoul can sense the thing that drives their paralysis dissipating from the victim. Alternatively, you could roll in secret and no one is allowed to know. It's all up to you, and the kind of game you want to play.
Good answers, thanks all!
Casters don't know the variable duration of their spells (CRB - Magic - Duration). I'd apply this to all abilities with variable durations. And targets shouldn't know either (and they shouldn't even know fixed durations for sure).
I agree with Khudzlin. Caster don't know the duration of variable duration spells, other creatures probably shouldn't know the duration of their variable duration abilities.