Standing Last In Line When they handed out Brains

One of my very best friends is divorced. Like, no big, so am I. But he, unlike me, gave marriage another shot and got remarried. To the same person. That was almost 3 years ago. This summer, he tells me that they are splitting up. AGAIN, for all the same reasons they split up the first time. THEN last night, while sitting on the couch, eating Cherry Chessecake Ice Cream and watching The Biggest Loser (define Irony) we start talking on the phone and he informs me that they are getting back together. AGAIN.

My reaction was as follows:

Friend: "Oh just FYI, Xtina and I are getting back together."
Me: "Oh HA HA. Very Funny."
Friend: "......."
Me: "Seriously. BAD JOKE, okay?"
Friend: "Not joking!"
Me: ".......Okay...........Stop messing with me! That's not funny!"
Friend: "You know my Brother had a similar reaction"

I told my friend that as long as he "knew what he was getting into" and was happy then I was cool with it. But when comes the point when being a good friend means NOT saying what they want to hear? Like "Hey, man. This chick is going to break your heart again and making you look like a chump. AGAIN." Is that on the 4th time around? Maybe the seventh?