How would the series have changed if Vinny was kept forever?

Remember when Brian was killed and got replaced by Vinny? That was 10 years ago!

How would the series have changed if Vinny was kept forever? I can't really say much about this, since it's been so long since I've watched the episode, but I can guess Family Guy would've lost a lot of its popularity as time went on. The Brian and Stewie relationship is just so cemented into the show that attempting to replace it would be suicide.