OK, I wasn't very clear... when I said "monsters", I meant mostly animals, or at least "irrational" monsters. I wasn't considering the Orcs as "monsters", in other words. And respawn may not be the best term either, but the world is certainly repopulated to a degree at the beginning of each chapter. And as far as I know, that only happens if you depopulate it first.
For example, if there's an area with a pack of wolves in Chapter I, there will probably be a smaller pack of wolves, or one of wargs, or maybe even a shadowbeast in its place when you get to Chapter II... but only if you've killed the wolves in Chapter I, IIRC. If you haven't, they will still be there, and the other monsters will not spawn till the beginning of the next Chapter. That's a fair bit of extra XP you're missing out on early in the game. Of course, I never once played through this game without combing the entire world for all the kills I could get in Chapter I, so maybe my memory serves me wrong?
As for my current playthrough, I'm still at Chapter I, now at level 13 and halfway to 14, and only now I've joined the Monastery. Soon I'll have a chance to check if I'm misremembering something; I'll be sure to come back here and tell you guys either way. :)
Post edited May 10, 2013 by Truehare