I think the base attitude is wrong here.

RP for the sake of just fun RP. If immexp is given, then that's nice. But don't count on it. Set your expectation to never be rewarded, instead see your interaction with the other players as a reward.

That said, I do think that long lived special characters that increase the fun for everyone should be given cabal edges or even quest forms etc. But it shouldn't be the reason you go and RP.