You'd get better/more replies if your thread title made sense. "Relationship rot" is rather gnomic and nobody can understand what it's about until you click and read the post.
BUT: This is a good idea, if it's personalized for each faction.
In some societies politics are fluid and administrations change a lot, and they would more quickly forget you. Look at Classical Athenian democracy and characters who were repeatedly elevated then exiled, like Alcibiades. Would also be true of the pirate dens' ever-shifting alliances.
In a dictatorship though, they'd forget almost nothing. For example, some authors whose books were banned during the Soviet Union are still banned in the successor states, long after the officials responsible have died of excess shashlik consumption.
Three values for each faction:
- A positive value beyond which good reputation wouldn't decay*
- A negative value beyond which bad reputation wouldn't decay*
- And an 'equilibrium' value after which the decay would stop (ie negative for pirates, neutral for most others)
(However, as the rep decays, the game shouldn't spam the player with messages about it, since it isn't directly related to their action)
*The player's actions of course, could still raise or lower the rep beyond these values.
This is another great way to differentiate factions, in addition to the idea of having them react differently to your actions; discussed in
this thread.