I have played rotationally for a while on my current game and haven't noticed too much mess, but then I do not write exact things down and my memory is not brilliant. But I do keep a photo album for each family, so I am aware that they still have marriage and best friend relationships intact and their jobs usually remain the same (except the self-employed - that is pretty annoying).
I thought all the culling problems had been fixed but I haven't played it since the last update so maybe they broke again? Or have I just been lucky and they were not fixed at all? I haven't had any unwanted romantic relationships appearing in marriages for a long, long time and mainly I just end up losing non-friend relationships and gaining some different non-friend relationships. I do get a few new bizarre friend relationships though, like my sims little boy being friends with some random creepy dude.