I could go for a fluff fic about the time Joe wondered if maybe Nicky was interested in other people. Nicky is a beautiful man, people flirt with him, and Nicky likes people (and all those things are also true about Joe but this is fluff logic, bear with me), maybe he wants to branch out. Maybe Joe's boring him? Maybe that's just a thing that's supposed to happen after the first three hundred years?

And then Nicky screws Joe's brains out because he's still 400% into Joe, the end.