The Daily Grind: Are rewards for offline time a good idea?

In City of Heroes Issue 13: Architect, a new 'day job' system will be introduced where your character can gain buffs and progress towards special badges without you having to arrest a single villain. The system just requires you to log the character out in a location appropriate to the kind of work your character does when he's not being a superhero – a University for a scholar, a Hospital for a medical technician, a Police Station for a cop – and when the character logs back in, you get an appropriate buff and badge progress.

Other games have 'rested' systems, too. Age of Conan has 'fresh kills', where a set number of the first kills of the day net you extra XP (so long as they're a challenge), and something similar was popularized in World of Warcraft long before.

But do these systems just reward players for not playing? Is a system that rewards you for spending time offline effectively dictating how you ought to play? Or do such systems enrich a game, giving added incentive to keep several alts on the go?