[Ide]

I'd be interested in some specific examples here, because most if not all of the time bonus systems I've seen don't work when you're idling, or it doesn't matter if you idle or not. You get RPXP when you RP obviously, so you're not idle there (unless you count waiting for the other person to respond as idling). Flat timed XP systems usually just award XP on a weekly or monthly basis (more typical in mushes, true), and the other timed rewards I've seen ignore idle/afk time in their calculation.

On the other hand maybe you have a different definition of idling -- does some common chitchat between characters count as idling? I'd say no, but if you say yes I can see your point.

I think timed bonuses have some good effects other than PR (which isn't a bad effect at all really). Mainly they partially level the playing field between people who have many hours to spend on a mud and more casual players. Usually casual players will get left out of the mix simply because they can't grind (or bot) for whatever reason, and I think in general a mud will do itself a disservice if it doesn't try to make a game good for casual players.

Of course some muds, RPIs maybe, won't care as much about casual players. But even in a RPI timed bonuses can help, as it can be difficult to adequately or semi-objectively reward the quality of someone's RP. A timed bonus is a neutral reward which benefits most PCs.