>D It's actually the second option--you get a rest bonus that adds up the longer you don't play. That is, so long as you leave your character in a city or inn/tavern (as noted when the level number next to your name has 'zzz' displayed).

So people that don't get to play much, have lots of rest bonus saved up--which means double exp for every kill so long as you have the bonus. Rather nice, does mean when you do get a chance to play, lots of exp and going up pretty fast, and the exp bonus lasts until you use it--doesn't have an 'expiration' time. : )