Collateral damage in a bad relationship

How many times have you watched one of your friends do nothing about 
their crappy relationship, or worse yet, rationalize either their own 
bad behavior or that of their girlfriend/boyfriend? My hit rate isn’t perfect, 
so I know how bad it sucks to be in said crappy relationship. However, what 
often gets lost in the muddle is the impact this has on the friends of the troubled 
couple. We must constantly endure story upon story about “how he did 
this” and “she did that” which, although annoying, wouldn’t be 
intolerable if it didn’t always end with “…but, he’s really a sweet guy” 
or “…but she only does this when she’s drunk”. And so it goes… Nothing 
changes. The cycle continues - They fight. You listen. They repent
You want to puke.

So, my question is, as a friend how long do you need to endure this agony 
before you either lash out and say something you’ll regret or simply decide that being friends isn’t worth it? I’d guess the answer will differ by 
person. The same people who can stomach a root canal for hours on end probably 
don’t mind one bit and are content to play Dr. Phil for evermore. On 
the other hand, people like myself who loathe complainers without 
solutions relish the thought of - in Facebook parlance - “de-friending” 
the offender the moment it becomes apparent s/he isn’t willing 
to make the effort to change things for the better.

For me, the watershed is usually after three major infractions within a year. Change or I’m history. It’s not sufficient that they promise not to talk about it 
with you (“I know this bothers you so I won’t talk to you about her”) 
because that’s a Faustian bargain. To some, this may sound harsh but I’ve also found, at least with good friends, this rebuke is often just the kick in the pants the person needs to get back on track.